Heating, Ventilation, and Air Conditioning (HVAC) is a system designed to regulate indoor climate for comfort and health. It includes three main functions: heating, which warms the air during cold weather; ventilation, which circulates fresh air and removes stale air; and air conditioning, which cools the air in hot weather. HVAC systems can be found in residential, commercial, and industrial buildings. They help maintain a consistent temperature and improve air quality by filtering out pollutants. Proper maintenance of HVAC systems is essential for efficiency and longevity, ensuring a comfortable environment year-round.