The main types of HVAC systems are split systems, packaged 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 and blower. Packaged systems are all-in-one units that contain all the components of a split system in one unit. They are typically used in smaller spaces and are more energy efficient. Ductless mini-split systems are similar to split systems, but they do not require ductwork and are more efficient than traditional systems. They are ideal for smaller spaces and can be used to heat and cool multiple rooms.