Long, short, pick like, rounded, all combs serve the same purpose, to help make beard grooming more simple.
Most are made with wide teeth for longer beards, to help clear tangles and knots. Others are made more fine-toothed for a shorter or more fine haired beard.
Most combs are hand made and are usually made out of wood, but others are made from plastic, metal or even bone or horns.

Just like with any products you buy, the more you pay for it the better it’s going to be and work for you, it’s the same with your comb.
The combs also hold small amounts of oil, so if your out and about with your comb you’ll also get a little bit of that oil that you put on earlier, leaving your beard smelling and looking great!