A condenser clothes dryer is a machine that looks just like a conventional tumble clothes dryer, but which does not require an external vent. For the user/owner, operation of both types of dryers is essentially the same - the difference is in the internal design.
How heat-pump clothes dryers work A traditional dryer works by heating air, blowing it into the drum chamber (where it absorbs moisture from the clothes), and then exhausting the now moisture-laden hot air out of the dryer and out of the house.
Vented dryers are the traditional type of dryer and are generally the cheapest to run as they use less energy than condenser dryers. Air is drawn from the surrounding area (i.e. the laundry room), then heated and blown through the clothes as the drum tumbles them about.