A dehumidifier works by trapping moist air, drying it up, and then expelling it back into the space. Now, dehumidifiers have coolant-filled coils that are built in every unit. Moist air is fan-forced into these coolant filled coils which then remove the moisture from the air. Depending on what dehumidifier you are using, the condensed moisture then drips into a bucket or pumped out of the unit through a built-in pump. The dried air is then expelled into the air. Note that different units are made with varying levels of sophistications. There are dehumidifiers with built-in pumps while most units have buckets that are called condensate buckets/basins.