A rooftop package unit refers to a type of HVAC system that is installed on the roof of a building rather than inside. These units contain all the necessary components for heating, ventilation, and air conditioning in one compact package, making them ideal for commercial and industrial buildings where space may be limited. Rooftop package units are often used in conjunction with ductwork to distribute conditioned air throughout the building. They offer advantages such as easy installation, accessibility for maintenance, and efficient operation.