Can you do it? Hold your thumb and middle finger together, relax your finger muscles, but hold your wrist. Then shake your hand so your index finger snaps against the middle finger. It sounds a bit like snapping your fingers, which in the U.S. can mean quickly as well, but is mostly a rude way to draw attention from a waiter or a dog, or a nice way to accompany singing.
I’ve been practising for a while now, but failed to achieve any result. My fingers remain silent. The best I got were barely audible pats. But it took me a while to learn to snap my fingers as well when I was a kid like this one. My colleague B. in the video reassured me that I’m not the only hopeless wannabee Brazilian. Perhaps I’d better try my luck with football?