I really liked this video by 3Blue1Brown explaining how blockchain works: https://youtube.com/watch?v=bBC-nXj3Ng4

Things that I didn't realize until I watched the video:

* "Mining" bitcoin means processing transactions for other people. Miners do time consuming operations to process transactions.

I had never heard of 3Blue1Brown before someone showed me that video, but he has a bunch of other good math videos. I liked the one about pi showing up in weird places.