This is a very interesting visualization of the fact that a number "abc" is mathematically 100a+10b + c (working in our standard base 10).
If you have 2 2-digit numbers of the form "ab" and "cd", their product is (10a + b)(10c + d) = 100ac + 10(bc + ad) + bd. If you see them do the computation, the cluster on the left corresponds to 100ac. There are two clusters in the middle that correspond to 10bc and 10ad and there is a cluster on the right that corresponds to bd.
Relevant : http://www.youtube.com/watch?v=a-e8fzqv3CE