What is Claude Code

An AI coding agent that runs in your terminal, inside your real project.

The Chat Tool Problem

A normal AI chat tool never sees your project. You paste code in, get an answer, then copy it back yourself. It cannot open your files or run your tests.

What Claude Code Does

It works directly inside your project folder. It can:

Read your files — the real code, not a pasted snippet
Edit files — you review each change before it is saved
Run commands — tests, linters, builds — and read the real output
Search your codebase — find where something is used, across many files

Example

You say:

“The login page hangs on a wrong password. Fix it.”

Claude Code finds the login code, reads it, finds the cause, shows you a diff, and runs your tests to check the fix. You approve each step.

Where It Runs

Terminal: type claude in any project folder
VS Code extension
JetBrains plugin (IntelliJ, PyCharm, WebStorm)

All three use the same tool underneath.

Made by Anthropic. Default model in 2026 is Sonnet 5, with Opus and Haiku also available — more on model choice later in this guide.

Next → Installation