The best primer I've seen is Andrej Karpathy's first video in his "zero to hero" series. It's worth following along with your own practice.

https://karpathy.ai/zero-to-hero.html

A while ago I had caught up with the basics thanks to the legendary 3blue1brown and his playlist on Neural Networks:

https://www.youtube.com/watch?v=aircAruvnKk&list=PLZHQObOWTQ...

and other helpers like Artem Kirsanov:

https://www.youtube.com/watch?v=SmZmBKc7Lrs