pumping milk for create a stash?

Kara
So I've looked up this topic before but I still don't get how women are producing this ginormous stash of milk. Some say they pump every 3 hours but how does that work when the baby wants to eat almost every 2-3 hours. And then if you pump after feeding not much comes out since u basically emptied them. Do you just have to be producing a big supply of milk?