A clothes dryer or tumble dryer is a machine that is used to remove water from clothing after it is washed. A dryer has a rotating cylinder called a "drum' that holds clothes and lets hot air in to evaporate the water. Then the heated air and water vapor exit through a vent. The drum spins so that the clothing stays apart making the hot air work better. Dryers can use electricity to both operate the machine and create heat to dry the clothes. Others use natural gas to create the heat.
Ventless clothes dryers work differently since they cannot vent the hot air. The two types of ventless dryers are condensation dryers and heat pump dryers. Condensation dryers heat the air the same as a regular dryer, but use a heat exchanger. The air is cooled and the water goes down a drain. A heat pump dryer works similarly but passes the air a heat pump. The water either goes down the drain or into a collection tank.