It is a standard way for Microsoft Window's applications to communicate with each other. Simple as that. You should already be used to this kind of thing. What is special about COM is that it provides a standard programming interface for this client and server communication. COM provides the low level guts for sharing this data and information back and forth.
Objects are a big deal in programming today.
Thus, objects are not just collections of database fields, but also have all of the smarts to understand how to manipulate it's own data. It really is. But because most people focus on the gory details, some people think it's hard. COM is fast. Windows uses COM all over the place.