Unlike the dishwasher or clothes washing machine, the dryer needs a little ongoing maintenance to keep it in safe, proper working condition.
How does a clothes dryer work? The way your dryer works is pretty simple - it spins clothes around in hot air while an exhaust vent sends damp air outside. A round, flexible exhaust tube connects to the back of your dryer and then to a duct in the wall that leads somewhere outside -- so all the hot, moist air coming out of the dryer ends up outside. As your heated clothes tumble in the hot air, lint (tiny bits of the cotton or other fibers that make up your clothing) comes off the fabric and most of it gets caught in the lint trap as the exhaust air passes through it.
The lint trap is usually accessed either inside the dryer door or on top of the dryer -- it usually looks like a plastic or wire screen. Whatever gets past the lint trap goes out the exhaust vent and duct and either clings to the sides of the tube (it is wet with condensation and can be sticky) or blows out the exhaust vent outside.