what is a binding? Is it what I THINK it is?... binding one's breasts to look male? "Cause the picture had me doing a double-take; the chest looks male

Yes. Under a regular shirt you can press them flatter with e.g. certain kinds of sports bandages or foundation garments designed for the purpose; with an open-shirt look like this, they're being taped outwards to the sides (you might notice you don't see any nipples where they would normally be).