In short Claude Code is an agentic coding tool that lives in the command line (and in editors). It doesn't suggest lines like autocomplete — it reads your codebase, runs commands and edits files itself, working through the agent loop. You set the task and steer.
How it differs from a chat assistant
A chat assistant answers in text: you copy code back and forth yourself. Claude Code is an agent: it has tools and permissions, it opens files, searches the project, runs tests, makes edits. The difference is between "asking for advice on the phone" and "letting an engineer into the project."
It runs the same loop as any agent (the agent loop and tools): gather context → act → check → decide the next step. It's bounded by the context window (what it sees, agent context management) and permissions (what it may do).
Where it runs
The terminal (its main home), VS Code and JetBrains (inside the editor), Claude Desktop (the app), the web (browser). The same agent, different shells. (These very notes are written by Claude Code.)
Three supervision modes
- Approval mode — before each action (edit a file, run a command) it asks permission. Maximum control, useful on the unfamiliar or important.
- Auto-accept — acts without stops. Fast, when you trust the task and its bounds.
- Plan Mode — first it builds a plan, shows you, and only starts after approval. The middle ground: you approve the intent without nudging every step.
Analogy: approval — an intern checking at every step; auto-accept — an experienced colleague you hand a task and leave alone; plan mode — a colleague who brings a plan for sign-off first.
Getting good results
- Frame the task and context clearly (prompting and AI Fluency).
- For anything serious — Plan Mode: check the intent before the code.
- Keep context in shape (
/compact,/clear,/context— agent context management). - Review changes with your own eyes (code review) before committing.
Next — the working rhythm Explore → Plan → Code → Commit and making it yours (Claude Code setup).
Related
The source is the Claude Code 101 course. Related: the agent loop and tools, Explore → Plan → Code → Commit, Claude Code setup, agent context management.