just a hobby baker. i was looking at commercial equipment today and i saw a proofer but never heard of one before. what does it do?

a proofer is where you put your bread to proof (raise). It is a kind of like an oven but it is set to a warm temp and it has humidity (water/steam) so that the bread raises quickly (30 min to 1 hour) and the humidity keeps the dough from getting a crust. It would be like when you do bread at home and set your oven to warm and put in a pan of water to make your bread raise quicker.

so a proofer is not necessary for baking cakes?

No. We use a proofer at the bakery for bread and pastries but not cakes.