Building automation system (BAS) and building management system (BMS) are related but different systems.
A BAS is a computer-based control system installed in buildings that controls and monitors the mechanical and electrical equipment such as HVAC, lighting and security. The main focus of a BAS is to improve the energy efficiency, comfort and safety of the building, while reducing operating costs.
A BMS, on the other hand, is a more comprehensive system that integrates all the subsystems of a building and provides a single point of control and monitoring. A BMS also known as building automation and control system (BACS) is a centralized system that controls and monitors all of the building's systems, including HVAC, lighting, security, fire protection and other systems. BMS also provides a user interface that allows building operators to view the status of all systems and make adjustments as needed.
In short, a building automation system focuses on the mechanical and electrical systems of a building, while a building management system is a more comprehensive system that integrates all subsystems of a building and provides a single point of control and monitoring.