Heating, ventilation, and air conditioning (HVAC) is a system used to control the indoor climate of buildings. It provides heating during cold weather, cooling during hot weather, and ventilation to ensure fresh air circulation. HVAC systems help maintain comfortable temperatures and improve indoor air quality. These systems consist of various components, including furnaces, air conditioners, and ventilation fans. Furnaces generate heat, while air conditioners cool the air. Ventilation systems help remove stale air and bring in fresh air, ensuring a healthy living environment. Proper maintenance of HVAC systems is essential for efficiency and longevity.