Attention instead of step-by-step
Older sequence models read text one token at a time, which made them slow and forgetful over long passages. The Transformer reads the whole sequence together and lets every token *attend* to every other — deciding, for each word, which other words matter most to its meaning. That single idea made models both faster to train on modern hardware and far better at long-range context.
It is the architecture underneath nearly all large language models and most current generative AI, and it has spread well beyond text into computer vision. When people say the field changed around 2017, the Transformer is what they mean.
The "T" you keep seeing
The T in GPT stands for Transformer. The architecture is the common ancestor of most models you interact with today.
