What Is Claude AI? Anthropic's AI Assistant Explained

*Originally published on [CodingCush](https://codingcush.com/what-is-claude-ai-explained).*

Claude is the AI assistant made by Anthropic, an AI safety company founded in 2021 by former OpenAI researchers. Like other top assistants, Claude answers questions, writes, summarises and codes, but it has built a particular reputation for careful, low-fluff answers, patient work with very long documents, and strong coding help. Anthropic trains Claude with a method called Constitutional AI, where the model is guided by a written set of principles it uses to judge and improve its own answers. If you want the thoughtful colleague rather than the loud one, Claude is usually the name people suggest.

Who Makes Claude?

Anthropic was founded in 2021 by a group of researchers who had previously worked at OpenAI, including siblings Dario and Daniela Amodei. The company focuses on AI safety research, and Claude is its main product. The Constitutional AI approach works like this: instead of only training the model on human ratings, Anthropic gives it a constitution, a list of principles about being helpful, honest and harmless, and trains the model to critique and revise its own responses against those principles. You can explore the current models on the [official Claude page at Anthropic](https://www.anthropic.com/claude).

Whether or not you care about the philosophy, the practical effect is easy to notice. Claude tends to admit uncertainty, avoids over-promising, and writes in a calm tone that suits professional work. It is the assistant many writers, researchers and developers open when the task is long and the details matter.


The official Claude pricing page on claude.com: Free, Pro, Max and Ultra, with Claude Code included on the paid plans.

The Current Claude Models (November 2026)

Anthropic's line-up has four tiers, and the whole family shares a very large 1 million token context window, which means Claude can hold entire codebases or book-length documents in mind during one conversation:

• **Fable 5.2**, released on 9 November 2026, is the top tier, built for the hardest technical work where you want maximum reasoning power.
• **Opus 5.5** is the recommended everyday default for most subscribers: very capable, and sensible for daily professional work.
• **Sonnet 5.5** is the balanced option, quick and smart in equal measure.
• **Haiku 5.5** is the fastest and cheapest tier, ideal for high-volume simple tasks.

A 1 million token window sounds like a spec-sheet number until you paste a 400-page PDF or a full project folder into the chat and Claude simply gets on with it. For document-heavy work, that is the feature people end up caring about most.

What Can You Do with Claude?

Beyond plain chat, Claude's feature list has grown into a small toolbox: