HVAC (Heating, Ventilation, and Air Conditioning) systems are designed to provide a comfortable indoor environment by controlling the temperature, humidity, and air quality. A ventilation system, on the other hand, is designed to provide fresh air to the indoor environment by exchanging stale air with fresh air from outside. HVAC systems are more comprehensive and include features such as air filtration, temperature control, and humidity control. Ventilation systems are typically simpler and focus solely on providing fresh air to the indoor environment.