This article provides a good explanation of how different publications and web sites use data. It distinguishes what Facebook and a few others do with your information from what most other web sites do. It also discusses how this affects publishers and the information available to you.
That’s not all. The Data Lords can also create something called ‘look alike audiences’, a key part of what Facebook (but by no means only Facebook) does. This means that the data may show that people with brown eyes, Toyota Camrys, fans of Katie Perry and chocolate milk buy the most fishing equipment and are the most intensely loyal readers of Fishing Times. Now the Data Lords can show your ads not only to Fishing Times readers (wherever they go on the web) but to this demographic profile which may seem to have no connection to fishing but yet has a demonstrated propensity to purchase fishing gear in the same way Fishing Times readers do.