Ad buying sounds complicated, but it really isn't that bad. The following platforms are here to help you once you know what they are and what their role is.
Demand Side Platforms (DSP)
DSPs allow advertisers to buy display ads across multiple ad exchanges through one interface. They also allow you to buy particular audience segments rather than specific website ad buys via real time bidding (RTB). DSPs use behavioral targeting data, collected from cookies (such as DoubleClick) and data exchanges, to identify audience segments. Once you define what kind of person you want to target, you define how much your are willing to pay per impression and the DSP will bid on ads that meet your criteria and serve your ads.
Supply Side Platforms (SSP)
SSPs allow publishers to sell display ads across multiple ad exchanges, DSPs, and advertisers through one interface. Often utilizing RTB, SSPs can maximize the value for each individual ad spot for the publisher. They are able to sell their impressions to the highest bidder, and access thousands of new advertisers that would likely not ever buy from the publisher directly.
Ad Exchanges provide a way for advertisers to run ad campaigns across multiple sites efficiently. Exchanges are automated platforms that facilitate transactions, kind of like a stock exchange, and are often used to move remnant and often low value inventory.
Ad Exchanges: Yahoo Ad Exchange,
Ad networks help advertisers who are trying to collect inventory from numerous websites and publishers by presenting a large collection of inventory so marketers can buy those impressions. In other words they collect inventory from many publishers and then mark it up and sell it.
The difference between an Network and an Exchange is that a Network is like a closed group of privately traded ads, an exchange could be compared to an open network where advertisers can see all of the impressions available. To better summarize - an Exchange can be seen as offering variety, while a Networks offers specialized groups of ads that meet the advertiser's needs.
Google AdWords is Google's online advertising program that lets you reach new customers and grow your business. AdWords can be split into 3 major pieces: Search, Display (GDN), and Video. Search allows advertisers to create ads that will run on targeted search on Google. Google Display Network (GDN) is an Ad Network that can only serve ads on Google's massive network of participating sites. Ads can be targeted contextually, by placement, topic, interest, or even by keyword, but only to sites within the GDN.