The way the clothes dryer use to works is really simple, it helps to spin the clothes all around in the hot air while the exhaust vent will also sends the damp air completely outside. On the other hand the exhaust tube will help to perfectly connects to back of the clothes dryer and also to the duct in wall that could also leads somewhere that is outside, so the hot as well as the moist air that is coming out from the dryer will finally ends up to be outside. Countries like Malaysia are especially prone to this kind of weather.
As the heated clothes will tumble in hot air the lint comes from the fabric as well as most of them will get caught in lint trap as exhaust air will passes through it. Now, you can also buy cloth dryers as lint trap is generally accessed either it is inside of the dryer door and it also on the top of dryer and it generally appears as like the plastic as well as the wire screen. What so ever gets the past with lint trap also goes out from exhaust vent as well as from duct and so they clings to sides of tube and even it blows out exhaust vent that is done outside.