What is the GPT model family?

GPT stands for Generative Pre-trained Transformer, and it's the family of AI models OpenAI builds — the same family that powers ChatGPT. Each word in the name tells you something real: Generative means it produces new text rather than just pulling up a stored answer, Pre-trained means it learned the patterns of language from a huge pile of text before anyone fine-tuned it for chatting, and Transformer is the neural network design underneath that lets it weigh how every word in a passage relates to every other word.

How we got here

The lineage starts in 2018 with GPT-1, a small research model almost nobody outside AI circles noticed. GPT-2 and GPT-3 got dramatically bigger and better at holding a real conversation, and GPT-3.5 was the version that launched ChatGPT into the mainstream in late 2022. GPT-4 was the next big jump, adding stronger reasoning and the ability to work with images, not just text.

Since then OpenAI has moved to a GPT-5 family with frequent numbered updates rather than one giant leap at a time — 5.1, 5.2, and onward through this year, each release splitting into faster everyday models and slower, more capable reasoning models. The old GPT-4 line has since been retired from ChatGPT entirely.

One family among several

GPT is only one of the major LLM families, not the only one. Google has its Gemini family, Anthropic has Claude, and Meta has Llama. They're all built the same general way — enormous amounts of text, transformer architecture, heavy compute — but each company trains and tunes its own family differently, so they end up with different strengths, tones, and price points.