# What is a transformer model in AI?

> A transformer is the neural network design behind ChatGPT, Claude and Gemini. It reads all the words in a prompt at once and weighs how they relate.

Source: https://learn.ynteractive.com/content/glossary/transformer-model · Updated 2026-10-20 · Free from Stepthrough (https://learn.ynteractive.com)

[AI basics](https://learn.ynteractive.com/content/glossary#topic-ai-basics) · [AI glossary](https://learn.ynteractive.com/content/glossary)

Quick answer

A transformer is the neural network design that today's large language models are built on. It reads every word in your prompt at the same time, works out which words matter to each other, and uses that to predict the next word of the answer. The "T" in GPT stands for transformer.

Last updated October 20, 2026

[Take the free module →](https://learn.ynteractive.com/courses/claude-jump-start/2)Module 2 of the free [Claude Jump Start](https://learn.ynteractive.com/courses/claude-jump-start) course, about 7 minutes. No account needed.

Updated October 20, 2026 · By [Robert Breen](https://learn.ynteractive.com/content/about)

## Why it matters for a small business

Google researchers introduced the transformer in a 2017 paper called "Attention Is All You Need". Older language models read text one word at a time and lost track of long sentences. Transformers look at the whole passage at once, which made it practical to train models on huge amounts of text, and that is what led to ChatGPT, Claude and Gemini.

You never set up a transformer yourself, but knowing the idea explains everyday behavior. The model writes by predicting likely next words, not by looking facts up, so a fluent answer can still be wrong. And because it weighs everything in the chat together, the facts and examples you include shape the answer directly.

## In a real lesson: Your First Chat with Claude: Models, Files and a Great First Prompt

In [Your First Chat with Claude](https://learn.ynteractive.com/content/claude-first-chat-tutorial), you open the model picker and see four Claude models: Fable for the toughest challenges, Opus for complex and everyday work, Sonnet for simpler tasks and Haiku for quick answers. Anthropic doesn't publish the full design of each one, but models like these belong to the family of transformer-based language models.

What matters for the lesson is the practical side. You attach Linda's complaint email as a file instead of summarizing it, so the model weighs her exact words when it drafts the reply. That is why Claude's draft names the sunken pavers and the debris, and flags the refund request for you to decide.

[Try this lesson free](https://learn.ynteractive.com/modules/claude-first-chat) or [read the step-by-step guide](https://learn.ynteractive.com/content/claude-first-chat-tutorial).

## Common confusions

### Transformer vs large language model

The transformer is the design. A large language model is a specific model, such as Claude Sonnet, built with that design and trained on a lot of text.

### Transformer vs the Python library

Hugging Face also has a popular code library called Transformers. It is a toolkit for developers, not the model design itself.

## Tips

- Give the model the real source text, such as the email or the policy, rather than your summary of it.
- Treat fluent answers as drafts: the model predicts likely words, it does not check facts.
- You don't need to know the architecture to pick a model; test the options on your own task.

## Related terms

[Large language model (LLM)](https://learn.ynteractive.com/content/glossary/large-language-model) · [Attention mechanism](https://learn.ynteractive.com/content/glossary/attention-mechanism) · [Neural network](https://learn.ynteractive.com/content/glossary/neural-network) · [Foundation model](https://learn.ynteractive.com/content/glossary/foundation-model) · [Token](https://learn.ynteractive.com/content/glossary/token)

## More AI basics terms

[Vector database](https://learn.ynteractive.com/content/glossary/vector-database) · [AI alignment](https://learn.ynteractive.com/content/glossary/ai-alignment) · [AI benchmark](https://learn.ynteractive.com/content/glossary/ai-benchmark) · [AI bias](https://learn.ynteractive.com/content/glossary/ai-bias)

## Where you use it: free lessons

- [Your First Chat with Claude: Models, Files and a Great First Prompt](https://learn.ynteractive.com/content/claude-first-chat-tutorial) (Claude, 7 min)
- [Prompt Writing 101: Role, Context, Task, Format](https://learn.ynteractive.com/content/prompt-writing-101-role-context-task-format) (ChatGPT, 8 min)

## Frequently asked questions

**What does GPT stand for?**

Generative Pre-trained Transformer: a model that generates text, is trained on a large amount of text first, and uses the transformer design.

**Do Claude and Gemini use transformers too?**

Today's leading large language models are generally built on the transformer idea, though each company keeps the details of its own models private.

**Do I need to understand transformers to use AI at work?**

No. It helps to know that the model predicts likely next words, so you give it real facts and check what it writes.

**Who invented the transformer?**

A team of Google researchers, in the 2017 paper Attention Is All You Need.

[All AI glossary terms, A to Z](https://learn.ynteractive.com/content/glossary) · [Free prompt templates](https://learn.ynteractive.com/content/prompts)