Glossary

What is GPT?

GPT is the family of AI language models made by OpenAI, and the models that power ChatGPT. The letters stand for generative pre-trained transformer. Generative means it creates text. Pre-trained means it first learned language from a huge amount of written material, and transformer is the type of design almost all modern language models use.

Why it matters for a business

GPT is the model and ChatGPT is the product built on it, so “we use GPT” can mean 3 different things: the ChatGPT app, OpenAI’s API that developers build on, or the same models served through a cloud platform such as Azure. Cost, data handling and control differ at each. GPT is also one of several leading model families, alongside Claude, Gemini and others, and for everyday drafting and summarising the top few are close enough that the product around the model matters more than the name. Inside ChatGPT, a custom “GPT” is something else again: a configured version of the app with its own instructions and files.