You're asking for a business primer, but you're referring (basically) technologies. The ads business is not driven by technology (maybe that is your realization?).

It sounds like you've heard of most of the acronyms, so what is it you think you're missing. ~90% of ad buys are auctioned CPC or reservation CPM. Direct and exchanges "big deals" but most ad startups attempt to optimize a component (in Google this kind of image: http://www.cogmap.com/blog/wp-content/uploads/2010/10/LUMA-D... was a classic "explanation" of the ads ecosystem). As you can see, serving is a small part, and the majority of that ecosystem works on reservation CPM or bid CPM.

My question to you is, if you know these tehnologies, what is your actual question (other than coming to grips with the complexity).