In a very badly and short as possible way, they are very complex probabilities machines, which can compare the probability of each words in your sentence to chose the words to say to you.
There is also Kyle Hill who explained how Chatgpt works in a video youtu.be/-4Oso9-9KTQ
however from what I remember I think the article has more info on how the tool manages to reduce confusion and history on the evolution with gpt 1, 2 and 3.
But what helped me understand easier was the video, even if it doesn’t describe every thing to the tiniest detail.