Font Licensing 101

I've perused a few font discussions, but I want to start at square one, just to make sure I have my head screwed in straight.

First, I use a MacBook Pro loaded with Adobe software, so I have access to fonts through both Apple and Adobe. I always assumed that, in the absence of obvious disclaimers, that these fonts were free to use in commercial products (e.g. websites, EPUBs, graphics, etc.). However, I was recently warned that I'd better go back and read the fine print.

So, my first question is how do I know if a particular font is Adobe or Apple?

Second, what are the rules for using Apple fonts? Can they all be freely used commercially, or do I have to track down the person who minted each font and purchase a license?

Thank you.