Condensation that builds up in refrigerator and freezer compartments is drained through a series of tubes into the drip pan to avoid frost accumulation inside of the unit. Once the moisture is in the drip pan, it is evaporated by the heat generated from the condenser.
If water is overflowing or leaking onto the floor from the drip pan, possible causes could be a clogged or frozen drain line, a cracked or damaged drip pan or a problem with the condenser fan.
The drip pan should be cleaned on a regular basis to eliminate the potential of mold growth. The health dangers of mold in the home are well documented, but it can produce an unpleasant smell as well.