The origianl dryer type was typically a vented style with a hose exiting to an outside vent hole and work by blowing hot air on your clothes. This produces moist air, which is then either vented out. Condenser dryers work by turning the moisture from your clothes into steam which is condensed into water and typically pumped to a water container which occasionally needs to be emptied and some include a drainage hose. This type of dryer is a good choice if you have a poorly ventilated laundry space. The dryer unit in a washer dryer is a condensor type which works in the same way bar the waste water is drained by the machines pump.