When mov­ing points and con­trol han­dles around in Illustrator I’m not think­ing about the math and num­bers the com­put­er is crunch­ing to cre­ate the curve I want. I’m just think­ing about what kind of curve I want. But this video is a great break­down of how things hap­pen. It’s not real­ly going to help you have bet­ter curves — there’s plen­ty of other places for that — but know­ing how your tools work is a sign of a good craftsmen.