A heating and cooling system—often called an HVAC system (Heating, Ventilation, and Air Conditioning)—is designed to control the indoor temperature, humidity, and air quality in homes, offices, and buildings so people stay comfortable throughout the year. In simple terms, it has two main jobs: Heating: During cold weather, the system produces warm air or hot water to raise the indoor temperature. This is usually done using a furnace, heat pump, or boiler. The warm air is then distributed through ducts or radiators. Cooling: In hot weather, the system removes heat from indoor air using an air conditioner or heat pump. The cooled air is circulated through vents to keep the space comfortable.