What Is Claude Code? Anthropic's Agentic Terminal Coding Tool

This article is written in English. Our training modules are available in French.

Have you ever wished for an AI assistant that doesn't just suggest code snippets, but actually understands your entire codebase, executes commands, creates files, runs tests, and commits changes—all while you describe what you want in plain English?

What Is Claude Code?

Claude Code is Anthropic's agentic coding tool that lives directly in your terminal. Unlike traditional AI coding assistants embedded in IDEs, Claude Code operates as an autonomous agent capable of understanding your entire project, executing multi-step tasks, and taking real actions on your codebase.

Launched in early 2025 and reaching general availability (v1.0) later that year, Claude Code represents a paradigm shift in AI-assisted development. It's not just an autocomplete tool—it's a thinking, reasoning, and acting coding partner.

The Terminal-First Philosophy

Claude Code embraces a terminal-first approach. Instead of being confined to an IDE panel or sidebar, it runs in your command line:

# Navigate to your project and start Claude Code
cd your-project
claude

This design choice is intentional. By living in the terminal, Claude Code:

• →Works with any editor: VS Code, JetBrains, Vim, Neovim, Emacs—whatever you prefer
• →Integrates naturally with Unix workflows: Pipes, scripts, and automation work seamlessly
• →Maintains full system access: Execute shell commands, run tests, manage Git operations
• →Stays out of your way: No IDE panels stealing screen real estate

What Makes It "Agentic"?

The term "agentic" is key to understanding Claude Code. Unlike passive AI tools that wait for you to ask questions, Claude Code can:

1. →Plan multi-step tasks: Break down complex requests into actionable steps
2. →Execute autonomously: Run commands, create files, modify code without constant approval
3. →Iterate on failures: If something breaks, it reads the error and tries again
4. →Maintain context: Understand your entire project structure and history

When you ask Claude Code to "implement user authentication with JWT," it doesn't just show you code—it:

• →Analyzes your existing codebase structure
• →Creates the necessary files
• →Installs required dependencies
• →Writes the implementation
• →Updates configuration files
• →Runs tests to verify everything works

How Claude Code Works

The Core Architecture

Claude Code connects to Anthropic's Claude models (Sonnet, Opus, or Haiku) through your terminal. When you start a session, it:

1. →Scans your project: Understands file structure, dependencies, and patterns
2. →Loads context: Reads your

   CLAUDE.md

   file for project-specific instructions
3. →Maintains conversation: Tracks your requests across the session
4. →Uses tools: File operations, shell commands, web searches, and more

Built-in Tools

Claude Code has access to powerful internal tools:

The Permission System

By default, Claude Code asks for permission before potentially destructive actions. You can configure this behavior:

• →default: Ask for approval on sensitive operations
• →plan: Read-only mode for exploration
• →acceptEdits: Auto-approve file edits
• →dontAsk: Auto-deny permission prompts
• →bypassPermissions: Full autonomy (use with caution)

Learn more about permissions in our guide on Claude Code Permissions: Deny, Allow & Ask Modes.

Key Features of Claude Code

1. Natural Language Commands

Describe what you want in plain English:

> Fix the TypeError in the user dashboard component
> Implement rate limiting for the API endpoints
> Refactor this function to use async/await

Claude Code interprets your intent, analyzes the relevant code, and implements the solution.

2. CLAUDE.md Project Memory

Every project can have a

CLAUDE.md

• →Project-specific instructions
• →Coding conventions
• →Architecture decisions
• →Things Claude should know about your codebase

# CLAUDE.md

## Project Overview
This is a Next.js e-commerce platform using TypeScript and Prisma.

## Conventions
- Use functional components with hooks
- All API routes should validate input with Zod
- Follow the existing folder structure in /src

## Important Notes
- Never modify the payment processing module directly
- All database changes require migrations

For a deep dive, see CLAUDE.md: Your Project's AI Memory File Explained.

3. Slash Commands

Claude Code offers built-in commands for common operations:

/init          # Initialize project with CLAUDE.md
/review        # Request code review
/compact       # Compress conversation history
/cost          # Show token usage
/memory        # Edit memory files
/mcp           # Manage MCP server connections

Explore all commands in our Claude Code Slash Commands Reference.

4. Model Context Protocol (MCP)

MCP allows Claude Code to connect to external tools and data sources:

# Add GitHub MCP server
claude mcp add --transport http github https://api.githubcopilot.com/mcp/

# Add your database
claude mcp add --transport stdio db -- npx -y @bytebase/dbhub \
  --dsn "postgresql://user:pass@localhost:5432/mydb"

With MCP, Claude can query your database, access Jira issues, read Figma designs, and more. Learn more in Model Context Protocol (MCP) for Claude Code: Complete Guide.

5. Sub-Agents and Parallel Execution

Claude Code can delegate tasks to specialized sub-agents:

• →Explore: Fast, read-only agent for codebase analysis
• →Plan: Planning agent for complex tasks
• →Custom agents: Your own specialized agents

> Research the authentication, database, and API modules in parallel using separate subagents

Discover more in Claude Code Sub-Agents: Orchestrating Complex Tasks.

6. Hooks for Automation

Hooks let you run custom scripts at specific events:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          { "type": "command", "command": "npm run lint:fix" }
        ]
      }
    ]
  }
}

Every time Claude writes or edits a file, your linter runs automatically. See Claude Code Hooks: Automate Your Development Workflow.

Real-World Use Cases

Building Features from Descriptions

> Add a feature that allows users to export their data as CSV. 
> Include a download button on the settings page.

Claude Code will create the export logic, add the UI component, wire up the API route, and test the feature.

Debugging Complex Issues

> The checkout process fails when users have items from multiple vendors. 
> Here's the error: [paste error]

Claude analyzes the error, traces through your code, identifies the bug, and implements a fix.

Codebase Exploration

> How does the payment processing work in this codebase?
> Show me the flow from checkout to order confirmation.

Claude reads relevant files, traces the execution path, and explains the architecture.

Git Workflow Automation

> Review my changes, create a well-formatted commit message, and push to a new branch

Claude runs

git diff

Legacy Code Modernization

> Migrate this class-based React component to a functional component with hooks

Claude understands the component's state and lifecycle, then refactors it while maintaining functionality.

Why Developers Choose Claude Code

1. Context Awareness

Unlike autocomplete tools that see only the current file, Claude Code understands your entire project—architecture, dependencies, conventions, and history.

2. True Autonomy

Claude Code doesn't just suggest—it acts. Need 20 files created with boilerplate? Done. Need to refactor across 50 files? Claude handles it.

3. Unix Philosophy

Claude Code is composable and scriptable:

# Watch logs and alert on anomalies
tail -f app.log | claude -p "Slack me if you see any anomalies"

# Automated translations in CI
claude -p "Translate new strings to French and create a PR for @lang-team"

4. Enterprise Ready

• →Data privacy: Your code stays on GitHub's runners (for Actions) or local
• →Compliance: Enterprise-grade security with AWS Bedrock and Google Vertex AI support
• →IAM integration: Managed permissions for organizations

5. Extensibility

Through MCP, Hooks, Plugins, Skills, and Custom Commands, Claude Code adapts to any workflow.

Getting Started

Ready to try Claude Code? Here's how:

Quick Install

macOS/Linux:

curl -fsSL https://claude.ai/install.sh | bash

Windows PowerShell:

irm https://claude.ai/install.ps1 | iex

NPM:

npm install -g @anthropic-ai/claude-code

First Session

cd your-project
claude

You'll authenticate on first run, then Claude Code is ready to help.

For a complete walkthrough, see Getting Started with Claude Code: Installation & Setup Guide.

Claude Code vs. Other AI Coding Tools

Wondering how Claude Code compares to GitHub Copilot or Cursor? Here's a quick overview:

For a detailed comparison, read Claude Code vs GitHub Copilot vs Cursor: 2025 Comparison.

Key Takeaways

1. →

   Claude Code is an agentic AI tool that lives in your terminal and takes real actions on your codebase—not just suggestions.

2. →

   Terminal-first design means it works with any editor and integrates with Unix workflows naturally.

3. →

   CLAUDE.md provides project memory, letting Claude understand your conventions and architecture.

4. →

   MCP, Hooks, and Sub-Agents extend Claude Code's capabilities to connect external tools, automate workflows, and parallelize tasks.

5. →

   Enterprise-ready with managed permissions, cloud provider support, and GitHub Actions integration for CI/CD.

Ready to Master Prompt Engineering for AI Coding?

This article introduced Claude Code and its capabilities. But to truly unlock its potential, you need to understand how to communicate effectively with AI models.

In our Module 0 — Prompting Fundamentals, you'll learn:

• →How to structure prompts for maximum clarity
• →Techniques to get consistent, reliable outputs
• →The building blocks of effective AI communication
• →Hands-on exercises with real-world scenarios

→ Explore Module 0: Prompting Fundamentals