Essentially, all exhaust fans are meant to expel moisture along with bad odors from a house. The differences arise from where each exhaust fan is placed. However, fans and moisture outlets mounted over kitchen range hoods are usually made of tougher material to withstand the heat.
While ceiling mounted exhaust fans expel moisture from the house upwards, in-line, and wall-mounted exhaust fans expel the moisture sideways. Just as the name suggests, exterior exhaust fans are installed on the exterior wall of a building. Interestingly, they do not push air to the outside; instead, they suck stale air from the inside and draw it out.
One major similarity in all exhaust fans is that they ventilate the house and rid it of excess moisture, consequently cutting down the cost of air conditioning. More importantly, they remove toxic substances from smoke, paint fumes, pesticides, cooking and contamination from other daily household activities. This goes a long way in keeping health hazards away, such as respiratory ailments.