What is the role of BACnet objects, properties, and services?

Objects: BACnet defines a number of object types used in building automation, such as "Analog value" or "Alarm and event". Each object type contains a predefined list of data points or attributes that describe a specific function. For example, an analog value object type can be used to describe the temperature of a room. These data points can be read or written by other BACnet devices, allowing interoperability between different systems.
Properties: Each object has a set of properties that describe and control it. These properties can describe, for example, the identity of the device, the type of the object, or the measured values of the object. BACnet defines a set of standard properties that must be included in each object type, but user-defined properties can also be added to meet specific requirements.
Services: BACnet defines a set of services that allow an object's properties and data points to be accessed and controlled. These services include reading and writing data points, monitoring alarms and events, and performing commands such as "power on/off". By using these services, different devices and systems in a building can communicate and interact with each other.