My brother referred these as "breezers", and I've seen them referred to as "shorts". But in the end, they're pants, and they usually reach down to your knees, like a nice pair of cargo shorts. Some hockey pants have protection up to the small of your back. The front usually has laces. I've seen players on TV cut their pants on the inseam, presumably to get more flexibility, but I've never needed that. A good pair of hockey pants should be snug at the waist, but the legs should be loose enough for the movement that you will be doing.
Hockey pants are typically worn with suspenders. There will be buttons in the front and back to fasten the suspenders. Practice putting these on at home so that when you're in a locker room full of players you can look like you can dressed by yourself! The suspenders themselves, while usually purchased separately, are almost always kept fastened to the pants. (I ended up owning two pairs of hockey pants. Buying these used or on consignment can usually be a good deal.)