What is COM?

Component Object Model is an architecture for component reuse that allows dynamic and efficient composition of systems from independently developed binary of components. 

~ Don Box

Basics

Books for Visual C++

Programming Visual C++ by David J. Kruglinski is the most popular one and Ivor Horton's Beginning Visual C++ but Kanithkar's Visual C++ Programming was the one that I began with.

Files and Purposes

• .sln file records information about the projects in the solution - names, relative paths, VS version used and configuration platforms such as debug/release defined for both solution and projects etc..
• .suo file, in which user options that apply to the solution will be recorded.
• .sdf contains data about IntelliSense for the solution. 
• .opensdf captures information about the state of the project. One would happen to see this file only while the project is open and disappears soon the solution is closed.

Reference(s)

MSDN

Ivor Horton's Beginning Visual C++ 2013