You're starting from zero. This chapter explains what Claude Code does, where to open it and what stays your job. You don't need to know how to code to follow along.
The idea in one sentence
Claude Code is Claude working directly in your project's files. You say what you want, it writes the code, runs it, reads the errors and fixes them.
The word for this is agent: a program that acts instead of only answering. It opens and creates files, runs commands, then shows you the result.
How it differs from the Claude chat or ChatGPT
With a chat, you copy-paste code between the conversation and your project. It works, but it's slow, and you have to explain your project again every time.
Claude Code sits next to you inside the project. It opens the files it needs on its own and edits them in place.
| What changes | Chat (claude.ai, ChatGPT) | Claude Code |
|---|---|---|
| Access to your project | You copy-paste | It reads and edits the files itself |
| Running the app, the tests | You do it yourself | It does it and reads the result |
| Errors | You copy them back into the chat | It sees them and fixes them right away |
| From one session to the next | You explain everything again | It rereads your instructions every time it starts |
The claude.ai chat can also run long tasks and hand you documents, spreadsheets or decks. To build an app or a website, use Claude Code. The full tour of the Claude apps is in the Claude Ecosystem guide.
Where to open it
Claude Code exists in several places, with the same subscription behind them. To get started, three options matter:
| Option | Who it's for |
|---|---|
| The Claude app, Code tab | Beginners. One app to install, no terminal, everything is in the window |
| VS Code with the Claude Code extension | If you want a real code editor next to the conversation |
| The terminal | Once you're comfortable: every command, automation |
My advice if you're starting out: the Claude app. In the Code tab, you see the files Claude edits, line by line, you get a preview of your app, and there's a built-in terminal if you ever need one. For a beginner, that does the job of a code editor.
This guide shows the first two options. Everything it explains also works in the terminal. There are other ways in (the web, your phone, Chrome) that you'll come across later. Installation is in chapter 2.
Words used in this guide
They come up in every chapter.
Claude Code is the tool: it reads your files and runs your commands. The model is what thinks and writes. By default it's Opus 5.5, and you can stick with it for the whole guide. The other models, and when to switch, are in chapter 19.
The unit of text a model reads and writes. A common word is often one token, while a long word or code takes several. Your subscription quota is counted in tokens: the ones Claude reads (the conversation, the open files) and the ones it writes.
Everything Claude has in front of it when it answers: the conversation, your instructions, the files it read. It has a maximum size. The fuller it gets, the more each message uses up, and the more likely Claude is to forget an instruction. Chapter 6 explains how to make room.
What it can do
Take a simple request: "Add a contact form to the home page."
- It reads your project. It looks at how your pages are built and reuses what's already there, your button style for example, instead of inventing a new one.
- The code comes next, in the files it needs. You see each change.
- Then it checks. It runs the app or the project's checks. If an error shows up, it reads it and fixes it before handing control back to you.
- Your rules are followed. Your conventions (interface language, colors, tools) are written in a file, the
CLAUDE.md, which it rereads every session. We create it in chapter 3.
On a big feature, it can follow a multi-step plan and check its work between steps. That's chapter 5.
Who does what
The pair works like a project manager teaming up with a developer. Claude writes fast and never gets tired of starting over. On the other hand, it has never met your users, and it doesn't know what matters for your business until you tell it.
What stays with you
- Describing what you want to build and why
- Making the call when Claude offers you several options
- Testing the app with a user's eyes
- Approving before anything goes live
What Claude handles
It writes the code, you don't need to type a single line. It suggests how to organize the project, runs the checks and fixes things until they pass. It also keeps the history of your changes (with Git, a tool we'll come back to) and explains its choices if you ask.
Question, action or plan
You ask a question: nothing gets changed, it explains.
"How does user login work in this project?"
You ask for a specific action, it does it right away.
"Add a 'Duplicate' button on each card that creates a draft copy."
For a big feature, ask for a plan first. You read it over, then it carries it out. It saves you a lot of rework (chapter 5).
"Suggest a plan for adding a booking system. Don't write any code yet."
What it's allowed to do without asking you
Claude acts on your computer, so a setting decides what it can do on its own: the permission mode. The four to know:
- Manual: it asks you before every change. The most reassuring way to start.
- Accept edits: it edits files without asking, but checks with you before running most commands.
- Plan: it reads and proposes a plan, without touching anything.
- Auto: an automatic check lets through what's safe and blocks what's dangerous, like deleting files in bulk or putting your site live.
In the Claude app, you switch modes from the mode menu (Cmd+Shift+M on Mac, Ctrl+Shift+M on Windows). In VS Code and the terminal, it's Shift+Tab. Details and fine-tuning are in chapter 9.
Question
You want to add a 'Pricing' page to your site. With the claude.ai chat, you'd copy the code into your files. What does Claude Code do instead?
Pick an answer to see the explanation.
Key takeaways
- Claude Code acts in your project: it reads, writes and checks the code. No more copy-pasting.
- To get started, the Code tab in the Claude app is enough. VS Code if you want a real editor.
- You decide and you test, it codes. The permission mode sets what it does without asking you.