An air conditioner is a system that is used to cool down a space by removing heat from the space and moving it to some outside area. The cool air can then be moved throughout a building through ventilation. A split system when there is an outdoor unit (the condenser) and an indoor unit (the evaporator). These two systems work together to accomplish the task of cooling an interior space while also dehumidifying it. This dehumidification happens as warm air from inside passes over the cold evaporator. The warm air condenses and loses moisture, just like warm air does on a cold glass of lemonade.