The Index

The error you get when a web page or API can't be found.

An AI that doesn't just answer — it takes actions, like reading files, running commands, or browsing the web, usually within limits you set.

The company that makes Claude.

A way for one piece of software to ask another piece of software to do something.

A long password that lets your code use a paid or private API.

Proving who you are to a website, app, or API.

How much the AI is allowed to do on its own without asking you first.

The part of an app the user doesn't see — the server, the database, the logic that runs behind the screens.

One of the most common shells. The default on most Linux machines and older Macs.

A parallel version of your project where you can try something without touching the version everyone else is using.

An update to a tool or library that forces everyone using it to change their code.

The app you use to open websites — Chrome, Safari, Firefox, Edge, and so on.

A mistake in the code that makes it misbehave.

Turning your project files into the packaged version that can actually run or be deployed.

A command that moves you into a different folder.

The consumer chat app from OpenAI, built on their GPT models.

A git command that switches you to a different branch, or to an older version of your files.

Automated pipelines that run your tests and deploy your code whenever you push changes.

An AI assistant made by Anthropic. One of the main AI tools people use for writing, coding, and reasoning through problems.

A version of Claude that lives in your terminal and can read, write, and run code on your computer.

The software making a request — usually your browser or an app you're using.

Making a copy of a project from GitHub onto your computer.

The method of controlling a computer by typing commands instead of clicking buttons.

A saved checkpoint of your work, with a short note explaining what changed.

The settings that tell a tool or app how to behave — things like which port to use, which database to connect to, how big to make the cache.

A self-contained, portable bundle of an app plus everything it needs to run.

How much text the AI can hold in its attention at once in a single conversation.

The language that describes how a web page looks — colours, fonts, spacing, layout, animations.

A spreadsheet-like text file where each row is a line and each cell is separated by a comma.

A code editor built on top of VS Code with AI baked in.

A program that stores your app's data in an organised way, so you can save, find, and update it quickly.

Figuring out why code isn't working and fixing it.

A bit of code your project needs that someone else wrote.

Putting your code somewhere the world can see it.

When a feature is marked as old and scheduled for removal, so you should stop using it.

A view of what changed between two versions — what was added, what was removed.

Another word for folder.

The phonebook of the internet — it turns a domain name into the actual address of a server.

A tool that packages your app and everything it needs — the runtime, the libraries, the config — into a single portable box called a container.

The name you type into a browser to reach a website — like google.com.

The app you type code into.

A way of turning a piece of text into a list of numbers that captures its meaning, so a computer can compare it to other pieces of text.

A specific address on an API for a specific thing you want to do.

A file where you list your environment variables in one place.

A setting the computer remembers outside your code — often used for secrets like API keys.

A message from the computer saying something went wrong.

Tests that check whether an AI system is actually doing its job well.

An add-on that gives your editor or browser extra powers.

The three or four letters after the dot in a filename. Tells the computer what kind of file it is.

The address of a file on your computer.

Taking an existing AI model and training it a bit more on your own examples, so it behaves the way you want.

Your own copy of someone else's project on GitHub, which you can change without affecting the original.

A larger piece of someone else's code that gives your project its overall shape, not just one helper job.

The part of an app you see and click — the screens, buttons, layouts, everything running in your browser.

A named chunk of code that does one specific job, which other code can call on whenever it needs that job done.

A tool that remembers every version of your project, so you can change things without fear of breaking them forever.

A website where people store, share, and collaborate on code projects.

A file that tells git to pretend certain files don't exist.

A family of AI models made by OpenAI. ChatGPT is the best-known product built on them.

A command that searches through text files for a word or phrase.

Rules or limits that stop an AI system from doing things it shouldn't.

When an AI confidently says something that isn't true.

Your personal base folder on the computer, where your files live by default.

Paying a company to run your code on their servers so the world can reach it.

The language that describes the structure of a web page — the headings, paragraphs, links, images, and layout.

The language web browsers and servers use to talk to each other.

An app for writing code that also helps you run it, test it, and fix it — all in one place.

What's happening when the AI is actually answering you, as opposed to when it was being trained.

Putting a tool or package onto your machine so it's ready to use.

The built-in list on a GitHub project where bugs, feature requests, and questions get tracked.

The programming language that runs in every web browser. Also runs on servers via Node.js.

A way of writing structured information so both humans and computers can read it.

A collection of ready-made code you can call on to do a specific job — date handling, image resizing, database access.

The rules about what you're allowed to do with a piece of code someone else wrote.

An automatic check for style problems, obvious mistakes, and risky-looking patterns in your code.

The kind of AI that Claude, GPT, and Gemini all are — trained on huge amounts of text to predict what comes next.

Your own computer. Where you're working right now, in front of you, before anything has been deployed or shared.

A special address that always means "this computer." When you open localhost in a browser, you're talking to a program running on your own machine.

A running record of what a program did, so you can look back and see what happened.

Tools that do most of the work for you but let you drop into code when you need to.

A command that shows you what's in the folder you're currently in.

The default, official branch of a project — the "real" version everyone agrees on.

A simple way of writing formatted text using plain characters — stars for bold, hashes for headings.

A shared standard that lets AI tools plug into other software — so an AI can read your email, update your calendar, or open your files without being hand-wired into each one.

Combining the changes from one branch into another.

When two branches changed the same bit of code in different ways, and git can't decide which to keep.

A command that makes a new folder.

The specific AI doing the thinking in a given product — Claude, GPT-5, Gemini, and so on.

A hosting service that deploys web apps from GitHub — close sibling to Vercel.

A framework built on top of React that handles the plumbing — routing between pages, loading data from servers, deploying to the web.

Tools that let you build apps by clicking and configuring, without writing code at all.

A program that lets you run JavaScript outside a browser — usually on your computer or a server.

The tool that installs packages for JavaScript projects, plus the huge online registry those packages come from.

A standard way to let one app access your account on another app without handing over your password.

Code released under a licence that lets anyone read, use, and change it — within whatever terms that licence sets.

The company that makes ChatGPT and the GPT models.

A bundled, named, versioned piece of reusable code you can drop into your project. Most often used interchangeably with "dependency."

The file in a JavaScript project that lists what it is, what it depends on, and what commands it can run.

The tool that installs packages for Python projects.

Text with no formatting, fonts, or styling — just the characters themselves.

A numbered door on your computer where a specific program is listening.

The live version of your app — the one real users are using right now.

What you type to an AI to tell it what you want.

The craft of writing prompts that reliably get good results.

Bringing the latest version of a project down from online onto your computer.

A proposal to merge your changes into someone else's project, with a place for them to review and discuss.

Sending your saved work from your computer up to a shared place online, usually GitHub.

A command that tells you which folder you're currently standing in.

A programming language known for being readable and beginner-friendly. Heavily used in AI, data, and automation work.

A technique where the AI searches your documents for relevant bits and reads them before answering, so it can speak about your specific stuff — not just what it learned in training.

A cap on how many times you're allowed to use an API in a given window.

A popular JavaScript framework for building the interactive part of websites — buttons, forms, anything that updates as you click.

The file at the top of a project that explains what it is and how to use it.

Replaying your commits on top of a different starting point, so your branch looks like it was built from the latest version of main.

Somewhere that isn't your computer — a server, a cloud machine, a GitHub repo online.

A project folder that git is watching.

The message your app sends when it wants something from an API or a server.

The message that comes back after you've sent a request.

The most common style for building APIs. REST APIs use web addresses (URLs) and standard actions like GET, POST, and DELETE, so different tools can talk to them the same way.

Reverting a deploy back to the previous version, usually because the new one broke something.

The environment your code actually runs in — the program or system doing the running.

A description of the shape that data is supposed to take.

A ready-made set of code and tools for working with a particular service, so you don't have to call its API by hand.

A computer whose job is to answer requests from other computers.

The program inside your terminal that reads what you type and runs it. Bash and zsh are both shells.

A way to safely log in to another computer and control it from your terminal.

A pair of files on your computer that proves it's you when you SSH into another machine — one file you keep secret, one you share.

A long error message that shows the chain of steps the program took before it broke.

A near-identical copy of your live app, used to test changes before they go to real users.

A way to temporarily put aside changes you haven't finished, so you can come back to them.

A short number in an HTTP response that says what happened. 200 means OK, 404 means not found, 500 usually means the server broke.

A word you put in front of a command to run it with admin powers.

A set of instructions that shape how the AI behaves for an entire conversation, before you've said anything.

A setting that controls how much the AI varies its answers — low temperature for consistent, predictable replies; high temperature for more variety and surprise.

The window where you type instructions to your computer instead of clicking.

A small piece of code that runs your code and checks whether it still works.

A small piece of text that an AI reads and writes in — sometimes a whole short word, sometimes a few characters, sometimes a chunk of a longer word.

When an AI reaches for a specific tool — like a calculator, a search engine, or your file system — instead of just talking.

The long, expensive process of teaching an AI by feeding it huge amounts of text or data before anyone ever uses it.

JavaScript with extra labels that say what kind of data each variable is. Helps catch mistakes before the code runs.

The full web address of something — the whole string starting with https://, including the domain and the path to the specific page.

A named container that holds a piece of data your code is working with.

A database built to store embeddings and find the closest matches quickly.

A hosting service that specialises in deploying web apps quickly, often straight from GitHub.

Building software by describing what you want to an AI in plain English, rather than writing the code yourself.

The most popular code editor in the world. Free, made by Microsoft.

A way for one service to call your app automatically when something happens — instead of your app having to keep asking.

Another way of writing structured information, designed to be easier for humans to read than JSON.

Another common shell, very similar to bash. The default on modern macOS.