How do sewing machines work?

I have been having trouble with my sewing machine recently.  It probably just needs a professional cleaning and adjustment but I may end up buying a new one.  So I have been looking around on the internet to educate myself in preparation for a possible purchase.

I have been using sewing machines for 45+ years but I never really understood how they worked inside.  I could never grasp how the top thread and the bottom thread got locked together in the bobbin.

But as part of my recent research into sewing machines I stumbled across the coolest little graphic that makes the process perfectly clear. It is so satisfying to finally understand what is going on in there!

I think this is so neat: