You can buy your ad inventory on the open exchange, or a private ad exchange. Most private exchanges are owned by premium publishers or vertical ad networks. It's important your know the difference.
Great description by IAB on programmatic variation and methods of buying. Here is an excerpt - "The terms "programmatic", "automation" and "RTB" evoke mean different things to different people. This paper aims to provide clarity, from the publishers' perspective, by outlining four main ways of transacting "programmatically" today. It provides a clear framework for distinguishing between them and highlights other factors commonly associated with each "programmatic"transaction.
At a high level, one key difference is that an Ad Exchange is a type of business or platform in digital advertising where RTB is a protocol for two digital advertising companies to transact. RTB was created as a protocol to connect the many different platforms of digital advertising namely Ad Exchange, DSP and SSP platforms
This is a great discussion by some advertising scientist responsible for designing the rules that matches a user with an advertiser. These algorithems are responsible for attribution, targetting in realtime bidding
When a user lands on a site whose inventory is sold through an exchange, what happens? How do exchanges integrate and apply targeting data from a data provider/data exchange? How do they handle all of this in a handful of milliseconds?