Below you will find a link to the AlphaGo documentary:
This link jumps to the section of the documentary that explains a little bit about how AlphaGo works.
The full documentary is really worth watching from start to finish.
An important part of the structure of AlphaGo is the Monte Carlo tree search. The video does not provide much detail on this, so in class I showed an example in greater detail to demonstrate how the tree search works. You can also find some discussion of this and some example code in the page I link to in the section below.
Here is a link to a blog post that provides some details on how AlphaZero works:
Here is a link to a video of a presentation by the head of the AlphaZero team, David Silver. In the video he discusses how AlphaZero differs from AlphaGo: