GPT as a LLM is trained on a foundation of text completion.
by relation of words as they come next (or most requently come next)
However transformers and attention changed this; But remements of their evolution remain - They will respons the same to prompts that they dont understand* (i use understand loosely)
But when they do understand, they are able to rephrase and reiterate.
Thats the closest we get to AI understanding words - but still… the most effective.