What is Claude? How It Differs from ChatGPT

If you've used ChatGPT, you already know what an AI assistant can do. Claude is Anthropic's answer to ChatGPT — a powerful AI assistant that takes a different approach to how it helps you think, write, and work.

Meet Claude

Claude is an AI assistant built by Anthropic, a company founded in 2021 by former OpenAI researchers Dario and Daniela Amodei. While ChatGPT launched in November 2022 and became the fastest-growing consumer app in history, Claude quietly built a reputation as the thinking person's AI — excelling at tasks that require careful reasoning, nuanced writing, and deep analysis.

The name "Claude" comes from Claude Shannon, the father of information theory. That choice reflects Anthropic's mission: building AI that processes information thoughtfully and reliably.

Claude's Model Family

Claude comes in several models, each designed for different needs:

Model	Best For	Speed	Intelligence
Claude Sonnet	Everyday tasks, writing, coding	Fast	Excellent
Claude Opus	Complex analysis, research, nuanced reasoning	Slower	Very high
Claude Haiku	Quick questions, simple tasks, high-volume use	Fastest	Good
Claude Fable	The hardest reasoning and long, multi-step projects	Slower	Highest

Claude Sonnet is the model most people use day-to-day. It handles writing, coding, analysis, and conversation with an excellent balance of speed and intelligence.

Claude Opus is for tasks that need deep reasoning, like analyzing complex legal documents or solving multi-step research problems.

Claude Haiku is the fastest model, ideal for quick tasks where you need answers without waiting.

Claude Fable is Anthropic's most capable model, for the most demanding work. It costs more to use, so most people reach for it only when Opus is not enough.

Each model gets a version number (for example, Sonnet 5.5), and Anthropic releases new versions every few months. You don't need to track them. The names Haiku, Sonnet, Opus and Fable stay the same, so everything in this course still applies when a new version arrives.

How Claude Differs from ChatGPT

While both are AI assistants, they have distinct personalities and capabilities:

Writing Style

Claude tends to write in a more measured, natural tone. Where ChatGPT might say "Absolutely! Here's an amazing breakdown of the top 10 strategies!", Claude is more likely to respond with "Here are several approaches worth considering, each with different tradeoffs."

This matters because:

• Claude's writing sounds less "AI-generated" to readers
• Professional documents feel more polished
• The tone is easier to publish without heavy editing

Context Window

The context window is how much text Claude can hold in one conversation. On paid plans, Claude's current models can hold up to 1 million tokens. That is roughly 750,000 words, or several long books at once. This means Claude can work with very long documents, or many documents together, without losing track of the details.

Other assistants also have large context windows now, so this is less of a difference than it used to be. It is still one of the main reasons people pick Claude for long documents.

Honesty About Uncertainty

Claude is more likely to say "I'm not sure about this" or "This is outside my training data." ChatGPT tends to give confident-sounding answers even when uncertain. Neither approach is always better, but Claude's transparency helps you know when to double-check.

Safety Philosophy

Anthropic built Claude using Constitutional AI (CAI), a technique where the AI follows a set of principles to guide its behavior. The goal is to be helpful, harmless, and honest. In practice, Claude is sometimes more cautious than ChatGPT about sensitive topics, though Anthropic continues to refine this balance.

What Claude Can Do

Here's a quick overview of Claude's capabilities:

• Write and edit — Articles, emails, reports, creative writing, code documentation
• Analyze documents — Summarize PDFs, extract data, compare multiple files
• Write code — Generate, debug, review, and explain code in many languages
• Answer questions — Research topics, explain concepts, provide analysis
• Process images — Analyze charts, read screenshots, describe photos
• Create artifacts — Generate interactive previews of code, documents, and visualizations
• Search the web — Look up current information and show you its sources
• Run code and create files — Analyze data, build charts, and make documents you can download
• Talk with you — Use voice mode on the mobile, desktop, and web apps
• Remember your preferences — Memory carries useful context from one chat to the next
• Reason through problems — Break down complex questions step by step

What Claude Cannot Do

Understanding the limitations is just as important:

• No image generation — Claude cannot create photos or artwork. It can make charts, diagrams, and simple visuals with code, and it can read images you upload
• Knowledge cutoff — Claude's training data stops at a certain date. It can search the web for newer information, but always check important facts
• Usage limits — Every plan has a limit on how much you can use Claude in a period of time. The free plan has the lowest limits
• Some features need a paid plan — For example, the Opus model, Research mode, and Claude Code

Why People Choose Claude

Different users gravitate to Claude for different reasons:

Writers choose Claude because its output needs less editing and sounds more natural.

Developers choose Claude because its code reviews are thorough and its explanations are clear.

Researchers choose Claude because it can analyze entire papers and books in a single conversation.

Professionals choose Claude because it handles long documents — contracts, reports, transcripts — without losing context.

Key Takeaways

• Claude is Anthropic's AI assistant, built with a focus on being helpful, harmless, and honest
• The main models are Sonnet (daily use), Opus (complex tasks), Haiku (speed), and Fable (the most capable)
• Claude's current models can hold up to 1 million tokens on paid plans, which makes it strong with long documents
• Claude's writing style is more measured and natural-sounding than ChatGPT's
• Claude can search the web, run code, and use voice mode, but it cannot generate images
• Claude is more transparent about uncertainty, which helps you know when to verify answers