Bathroom ventilation is required by law to prevent the buildup of mold so ducted ventilation is one option people have. Other ventilation options are windows and fans that blow the air into another room. Based on where your bathroom is located in your home, you may have no other options except ducted ventilation.
Wall fans blow air from the bathroom into the room on the other side of the wall, then sucks the clean, dry air back into the bathroom. This keeps it from getting too steamy so mold doesn't build up. This type of ventilation only works if the bathroom is next to a wall that is a part of an open space on the other side. For example, if the bathroom wall is connected to a wall that the hallway is also connected to, you can put the fan here so it blows out into the hallway. However, the wall can be indoors or outdoors. If the fan pulls in air from outside, you must properly insulate it so that it isn't drafty.
A window is a simple option. You don't have to worry about any electrical wiring or mold buildup because it is a direct path to the outdoors. This only works if your bathroom has an outside wall. Put the window up high so no one can look inside.
Exhaust fans are the same thing as duct fans because a duct is attached to the exhaust fan, which sucks the air out of the room. These fans have alternative versions though. One way they work is to emit the moist air into the attic. This however, can cause mold over time. Another way is to have the duct go through the attic and out of the roof. The third way is for the duct to go through the walls and emit the air outside of the house through a vent.