There are four main types of HVAC systems: split systems, packaged systems, hybrid systems, and ductless mini-split systems. Split systems are the most common type of HVAC system and consist of an outdoor unit and an indoor unit. The outdoor unit contains the compressor, condenser, and expansion valve, while the indoor unit contains the evaporator coil and air handler. Packaged systems are similar to split systems, but the components are all housed in one unit. Hybrid systems are a combination of split and packaged systems, and are designed to be more energy efficient. Lastly, ductless mini-split systems are a type of split system that does not require ductwork and can be used to heat and cool individual rooms.