GPT-3, GPT-4, ChatGPT... These letters are everywhere. But what do they actually mean? Behind the acronym lies an architecture that changed the world of AI. Here's what you need to understand.
The acronym broken down
GPT = Generative Pre-trained Transformer
Three words, three fundamental concepts:
The Transformer — the invention that changed everything
Before 2017, language AIs processed text word by word, in order. Slow and limited.
The Transformer (invented by Google researchers) introduced a mechanism called "attention": the model can look at all the words in a sentence at the same time and understand their relationships.
Concrete example:
In the sentence "The cat that was on the mat fell asleep", a Transformer understands that "fell asleep" relates to "cat", not "mat". Older models struggled with this.
Why it matters:
This ability to grasp global context is what makes current LLMs so powerful. Without the Transformer, no ChatGPT.
Pre-trained — the massive training
"Pre-trained" means the model learned from data *before* you use it.
The numbers are staggering:
What this implies:
Generative — token-by-token generation
A GPT model doesn't "think" then write. It generates one token at a time, predicting the most probable at each step.
In practice:
When you ask a question, the model:
This is why:
GPT vs the others (Claude, Gemini, Llama)
GPT is the name of OpenAI's models. But the Transformer architecture is used by all:
The difference isn't in the base architecture, but in:
In summary: "GPT" has become a generic term, but technically it's the OpenAI brand. The others are "cousins" that share the same foundations.
Why understanding this matters
Knowing what GPT means helps to:
1. Demystify
It's not magic; it's statistical engineering at massive scale.
2. Understand the limits
A pre-trained model only "knows" what it has seen. Nothing more.
3. Use it better
Knowing that the model generates token by token explains why prompt wording matters so much.
4. Avoid the nonsense
When someone says "our revolutionary proprietary AI", you know it's probably a Transformer like the rest.
Key takeaways
- -GPT = Generative Pre-trained Transformer.
- -The Transformer (2017) is the architecture that changed everything thanks to the attention mechanism.
- -"Pre-trained" = the model learned before you use it, on frozen data.
- -"Generative" = it produces text token by token, predicting the next one.
- -Claude, Gemini, Llama use the same base architecture — the differences are in the details.