What is a ductless bathroom fan?

Answer: Bathroom without a fan

Answer: Pulls air through a charcoal filter

Answer: An exhaust fan

Answer: An exhaust fan that doesn't exhaust the air out of the house.

Answer: Fan without ducting and uses a filtering system instead.

Answer: A Ductless fan is meant to pull moisture out of a bathroom, not really deal with odors. For odors they sometimes can be equipped with a carbon filter. It is intended to give a bit of negative pressure, but is definitely one of those "not a very good idea" designs.

Answer: Circulation fan

Answer: A fan that doesn't need to be ducted to the outside

Answer: Not sure

Answer: Special Duct Work is not required

Answer: It comes with a filter and does not comply with local codes.

Answer: one without a duct or installed in a window

Answer: a fan that exhaust back into the room

Answer: It's a fan which has no duct work attached. It is meant help draw away bad odors when there is not room for duct work. They are really not very effective frankly.

Answer: used for 1/2 baths or where there is no moisture