GPT

Decode the letters

G is for Generative. It creates new text rather than picking from canned replies.

P is for Pre-trained. Before you ever talk to it, it spent months learning from a mountain of text. By the time you arrive, the studying is done and you get the finished student.

T is for Transformer, the 2017 invention that made all this work. It is a design that lets the model weigh every word in your message against every other word at once, so it does not read one word at a time and forget the start of the sentence.

GPT vs ChatGPT

GPT is the engine. ChatGPT is the car built around it: the chat app, the safety layer, the web search. OpenAI names its engines GPT-something, like GPT-5.6, and the app stays ChatGPT.

Other companies build the same kind of engine with different names: Anthropic's Claude, Google's Gemini, xAI's Grok. People sometimes say "a GPT" for any of them, like saying "googling" for any search.