Answer:
As the cooling (evaporator) fins cool down the air, it causes the air’s dew point to drop and moisture to form on the fins (like on the outside of an iced drink’s glass). this drains to the bottom of the AC. The Air Conditioner should tilt a little toward the outside so the water will drain outdoors. Your unit probably doesn’t have such a tilt, so water drains inside. Tilt your AC toward the outdoors a little so that the water will drain outdoors.