What is Claude?
Claude is an AI assistant made by Anthropic, a safety-focused AI company founded in 2021. Claude can read, write, analyze, code, summarize, translate, and reason through problems — much like ChatGPT, but with a different emphasis on safety, nuance, and long-context understanding.
Claude is available on claude.ai (free and paid plans), via the Anthropic API (for developers), and as Claude Code (a CLI tool for software engineers). Each interface gives you the same underlying model but different capabilities.
The name “Claude” comes from Claude Shannon, the mathematician who founded information theory — a nod to Anthropic's research roots.
claude.ai
Web interface. Free tier available. Start here if you're new.
Anthropic API
For developers. Access Claude programmatically in your apps.
Claude Code
CLI tool for software engineers. Runs in your terminal and IDE.
Claude Models Explained
Anthropic releases Claude in three tiers. Think of them as the same brain at different speeds and price points.
Claude Opus
Most capableSpeed: ★★☆☆☆ · Cost: $$$$The smartest Claude model. Best for complex reasoning, nuanced writing, multi-step analysis, and tasks where quality matters more than speed.
Best for:
- Complex research & analysis
- Long-form writing
- Advanced coding
- Strategic planning
- Multi-step reasoning chains
Claude Sonnet
Best balanceSpeed: ★★★★☆ · Cost: $$$The everyday Claude. Sonnet is fast, smart, and cost-effective — the right choice for most tasks. It's what most users should default to.
Best for:
- Everyday writing & editing
- Code generation
- Q&A and explanations
- Summarization
- Customer support drafts
Claude Haiku
Fastest & cheapestSpeed: ★★★★★ · Cost: $Ultra-fast and low-cost. Haiku handles simple tasks at scale — ideal for classifying, tagging, short responses, or high-volume pipelines.
Best for:
- Classification & tagging
- Simple Q&A
- High-volume automation
- Real-time responses
- Form validation & routing
Which model should you use?
Start with Sonnet for everything. Switch to Opus when you need deeper reasoning and Sonnet isn't cutting it. Use Haikuwhen you're building an app and need to process thousands of requests cheaply.
How Claude Works — Prompting Basics
Claude works through conversation. You write a message (called a prompt), Claude responds. The quality of your output depends almost entirely on the quality of your input.
System prompt (optional, powerful)
A hidden instruction that shapes how Claude behaves for the entire conversation. Used to give Claude a role, set rules, define output format, or restrict topics. This is what AI agents use.
User message
Your actual question or task. The more specific and structured, the better the output.
Claude's response
Claude reads both the system prompt and your message, then generates a response that follows all constraints it has been given.
Context window
Claude remembers everything in the current conversation up to its context limit (200,000 tokens for Claude 3.x — roughly 150,000 words). Beyond that, older messages are forgotten.
What Are AI Agents?
An AI agent is Claude with a specific identity, role, and ruleset baked in from the start. Instead of asking a generic AI a question, you give Claude a system prompt that makes it behave like a specialist.
Generic Claude vs Agent Claude:
❌ Generic prompt
“Help me grow my startup”
Vague answer. Generic advice. No framework.
✅ With Growth Hacker Agent
“Help me grow my startup”
Analyzes funnel, identifies biggest leverage points, gives a 30-day experiment roadmap with metrics to track.
How to use an agent — 3 steps:
- Pick an agent from the library (or write your own system prompt)
- Start a new conversation in Claude.ai, ChatGPT, or any AI tool
- Paste the system prompt as your first message — then give your task
On this site we have 150+ free agents for marketing, coding, sales, design, research, and more — all ready to copy and paste.
Browse free agents →What Are Skills?
Skills (in Claude Code — the CLI tool) are reusable slash commands that trigger a pre-defined workflow. Instead of typing the same complex prompt every time, you type /skill-name and Claude executes a complete, structured task.
Example skill invocations:
/review # runs a full code review on the current branch
/seo # audits current page for SEO issues
/init # creates a CLAUDE.md file documenting your codebase
/security-review # checks for security vulnerabilities
Skills vs Agents
Agents define WHO Claude is (persona, rules). Skills define WHAT Claude does (specific task workflow). They work together — a code reviewer agent + a /review skill.
Skills vs Commands
Commands (/help, /clear, /model) control the Claude Code app itself. Skills (/review, /seo) run custom AI-powered workflows you or someone else defined.
Built-in skills
Claude Code ships with built-in skills like /review, /init, /security-review. These are professionally designed workflows ready to use.
Custom skills
You can create your own skills in .claude/commands/ as markdown files. Write the prompt once, use it forever with a single slash command.
Claude Code Commands Reference
These are built-in slash commands that control Claude Code itself — not AI workflows, but app-level controls. Type them directly in the Claude Code terminal.
/helpShow all available commands and how to use them.
/clearClear the conversation context and start fresh.
/modelSwitch between Claude models (Opus, Sonnet, Haiku) mid-conversation.
/saveSave the current conversation to a file.
/memoryView or edit what Claude remembers about you across sessions.
/settingsOpen Claude Code settings to configure behavior, permissions, and hooks.
/reviewRun a code review on the current branch or pull request.
/initInitialize a CLAUDE.md file with documentation for the current codebase.
/mcpManage MCP (Model Context Protocol) server connections.
/costShow the token usage and cost estimate for the current session.
/compactCompress the conversation context to save tokens while preserving key info.
/bugReport a bug or issue with Claude Code directly to Anthropic.
6 Prompting Tips That Actually Work
These techniques work in Claude, ChatGPT, and any other large language model. Master these and you'll get dramatically better output.
Give Claude a role
Start your prompt with "You are a [role]" — Claude will adopt that persona and respond differently. "You are a senior security engineer reviewing this code for vulnerabilities" gets better output than "check this code."
Be specific about the output format
Tell Claude exactly what you want back: "Give me a bullet list", "Write this as a JSON object", "Format as a markdown table with 3 columns". Vague requests get vague output.
Use examples (few-shot prompting)
Show Claude one or two examples of what you want before asking. "Here is an example of the style I want: [example]. Now write one about X." This is the single most effective prompting technique.
Chain tasks step by step
For complex tasks, break them into explicit steps: "First, list the problems. Then, rank them by severity. Then, suggest a fix for the top 3." Claude follows sequential instructions better than open-ended ones.
Ask Claude to think before answering
For reasoning tasks, add "Think step by step before giving your answer." This activates Claude's extended thinking and dramatically improves accuracy on math, logic, and analysis.
Set constraints
Tell Claude what NOT to do: "Don't use jargon", "Don't exceed 200 words", "Don't suggest paid tools". Constraints shape output as much as instructions do.