In April, Google announced its $3.1 billion acquisition of DoubleClick. It was treated as Big News and generated lots of press but I found it hard to understand what the deal meant to Google and its competitors. Clearly it meant a lot to Microsoft, which paid $6 billion in May to acquire Acquantive – another name unknown to consumers having something or other to do with online advertising.

A Google product manager has written an overview of the world of online advertising and an explanation of why Google purchased DoubleClick. It’s got a bit of history and some figures that shed light on how things work in the online advertising economy. You might still be confused when you finish, but you’ll be confused at a higher level, which is about all we can hope for these days.