Claude Code is an agentic coding tool that runs in your terminal. You give it a task in plain English and it reads your codebase, edits files, runs shell commands, writes tests, and creates commits instead of just suggesting what you might do.
I'll compare it to the tools you probably already use. A code autocomplete tool waits for you to type and fills in the next few tokens. Claude Code takes a description like "add rate limiting to the API" and works through your entire project to make it happen. You stay in the loop through a permission system that asks before anything risky.
You run it from any terminal with the claude command, so you don't need an IDE.