.claude/settings.json is where you configure Claude's behavior for your project. It sits in .claude/ alongside your skills and rules, and you can commit it so the whole team shares the same setup.
Your personal global settings live at ~/.claude/settings.json. Project settings override user settings where they conflict.
I'll show you the main top-level fields: permissions (what Claude can and can't do), env (environment variables to inject), and hooks (lifecycle automation). You'll rarely need more than these to cover most configuration needs.