These are not traditional ceiling fans with exposed blades and lights, rather they mount inside the ceiling and duct to the attic or outside to vent bathroom moisture and odors. Many include a light fixture, a night light, a heat lamp, and/or a heater. To install one you have to cut a hole in your ceiling if it is not already prepared. If you install a model with more than just a fan, or fan and light (if you don’t mind the fan and light switching together) you will also have to install additional wiring. Installing a bathroom fan is a project best left to an electrician unless you are very handy.
Here are some common brands of bathroom ceiling fans:
Air King
Broan
Hunter
Nautilus
Nutone
Panasonic Ceiling Fans