Andrew Ng's courses on Coursera are helpful to learn about the basics of deep learning. The "Generative AI for Everyone" course and other short courses offer some basic insight, and you can continue from there.
This Intro to Transformers is helpful to get some basic understanding of the underyling concepts and it comes with a really succint history lesson as well. https://www.youtube.com/watch?v=XfpMkf4rD6E
thank you, the replies to your comment are far better than this marketroid rubbish that doesn't even tell you how to run a generative ai, much less write one