HVAC units can be divided into two main categories: central and split systems. Central systems are typically used in larger buildings and are composed of a single unit that is connected to ducts that distribute the air throughout the building. Split systems, on the other hand, are composed of two separate units: an outdoor condenser and an indoor air handler. The condenser is responsible for cooling the air, while the air handler is responsible for circulating the air throughout the building. Both systems are designed to provide efficient and effective climate control.