A condensing dryer has a tube or bladder of cold water that the hot exhaust from the dryer drum will be directed against; the moist lint-filled air will condense back to water when it hits the cold surface. Usually, cold water is flowing continuously and the outflow water from the condesor tube will wash away the accumulated lint.
I am still working on a GE washer/dryer combo that is a condensor style - I tried to learn as much as I could about this type of dryer, but I may not have all the facts here...