Yes, I wanted to comment that it's just taking dot products of the rows of the left matrix and the columns of the right one. That's also more easy to understand

Yes, I wanted to comment that it's just taking dot products of the rows of the left matrix and the columns of the right one. That's also more easy to understand since there's just one thing going on at a time, and you don't have to move, flip and overlay matrices. This is nice to animate but almost impossible to do in your head.