Core concepts
GPT
Generative Pre-trained Transformer — the architecture behind OpenAI's models, and now used as shorthand for any LLM-powered chatbot.
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In plain English
GPT stands for Generative Pre-trained Transformer. It's both the technical name for the architecture OpenAI uses (GPT-2, GPT-3, GPT-4, GPT-5) and a generic term most people use to refer to LLM-based chatbots in general.
Breaking down the name:
- Generative — produces new text rather than classifying
- Pre-trained — trained on massive text data before being released
- Transformer — the underlying neural network architecture
Why GPT became famous: ChatGPT (built on GPT-3.5 and later GPT-4) was the first AI product to reach 100 million users in two months. It made LLMs mainstream and reset what consumers expect from software.
Other LLM families (Claude, Gemini, Llama) use the same transformer architecture but aren't technically "GPTs" — though many people use the word loosely for any chatbot.
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Related terms
LLM
Large Language Model — the type of AI behind tools like ChatGPT and Claude, trained to understand and generate text.
Transformer
The neural network architecture introduced in 2017 that powers nearly every modern LLM, image generator, and AI breakthrough.
Generative AI
AI systems that create new content — text, images, audio, video, or code — rather than just classifying or predicting from existing data.
Foundation Model
A large, general-purpose AI model trained on broad data that can be adapted (via prompting or fine-tuning) to many downstream tasks.
AI Assistant
A conversational AI tool that helps users with tasks like writing, scheduling, research, or answering questions in natural language.
Back to glossaryLast reviewed May 2026