Venting a bathroom properly is maybe the most important consideration one has to make, as bathroom is likely to be the single biggest source of moisture within a house. Hence, there may even be a building code requirement in your city for this.
Moisture that stays in the bathroom can potentially cause problems like mold and mildew, enlargement or cracking of vanity plywood, a smell that weird, chipped wall paints to peeled wall papers.
A proper ventilation of the bathroom using a bathroom ventilation fan will exhaust excess moisture and keep it drier. Bathroom ventilation fans pull moisture filled air, as well as bathroom odors and vent it outside the house using the connected vent.
There are several types of Bathroom Ventilation fans to choose from based on your specific bathroom requirement. Most of the bathroom fans are simple and do the job, but you can find feature loaded bathroom fans as well. For example bathroom fans with built in motion sensors that turns the on/off the fan based on occupancy. Also there are fans that's a fan/light fixture combination or the ones that have built-in speakers.
However, the key features to look for in the a bathroom ventilation fan is its CFM and Noise Level (sones).