It is only through its properties that an object is monitored and controlled. Both are associated with the space temperature read from a physical input. When you reference the data point, however, typically the only thing that it indicated was the room temperature, perhaps 72. The AI object also reports the room temperature as 72. As you can see, the AI object is much more robust than the data point.
All objects have some required properties and some that are optional.
As indicated in the discussion of objects above, objects are monitored and controlled only through their properties. BACnet specifies 123 properties of objects. BACnet also may require that certain objects support specific additional properties. The type of object and the type of device in which that object resides determine which properties are present. Some properties can accept writes, and others can only be read.