COM enables components to be reused at a binary level, meaning developers do not require access to the source code of ArcObjects in order to extend the ArcGIS platform.
The ArcObjects data model is based on the COM standard, which makes it compatible with other COM objects and applications.
The ArcGIS platform was built using ArcObjects types, such as classes, interfaces, and enumerations.
ArcObjects use COM interfaces to organize and communicate properties and methods of its classes, ensuring compatibility with other COM-based objects and systems.
For example, it is possible to query for additional interfaces implemented by an object after instantiation via the process of QI.