This Photoshop photo contains
boater, leghorn, panama, panama hat, sailor, skimmer, straw hat, fedora, felt hat, homburg, stetson, trilby, and snap brim hat.
There might also be
pith hat, pith helmet, sun helmet, topee, topi, cavalier hat, and slouch hat.
First we will quickly go through Layers, since you can not understand what a mask is or does before you understand what a layer is. After that, we'll continue to learn what a mask is, when & how we use it, and a few shortcuts and tips.