If I go to the library and check out a CD; is that stealing?
No. That's "fair use" borrowing. (Have you ever heard of the concept of "fair use"?)
If I put the music from the aforementioned borrowed CD onto my MP3 player; is that stealing?
Yes. You are now copying - i.e. duplicating. That's where the infringement comes into play.
If I'm at work listening to my MP3 and a buddy wants to listen too, and so I load the music onto his MP3; is that stealing?
Yes. You are now copying - duplicating - and you are now making your buddy an accessory to the infringement.
My buddy likes the music so much, he decides to burn it onto a CD so that he can listen to it in his car. Is that stealing?
Yes, since he's duplicating already infringed work.
NOW, if your buddy had bought that CD and made one copy for himself on another medium, that is considered acceptable use (typically "fair use" - yet another copyright LAW concept).
I may be wrong but doesn't infringement only come into play when you re-sell the item you duplicated? Private gifting between individuals should be okay.
What if I give my buddy a 'gift' of 10 mp3s, burned off an original CD?
Or, what if I give my buddy the original CD, and keep the 10 mp3s for myself?
Copyright is dead. The issue is control of access.