DLL vs COM

[Daljeet]

I am new to COM so please clear my doubt.

As per "Inside COM" one should not compare dll's with COM stil, I have one question-

"What extra COM dll or COM provides over a simple dll and what are the differences among the two."

Please explain and suggest some good books for this.
Thanks.

[sanandikar]

Dll is like exe
COM is a communication protocol bet objects
so i think they can not be compared