[belorn]

It is about so much more. It is any personal data that facebook store that is not strictly necessary to provide the core products (such as messaging or sharing content).

You bought some medicine online and the store shared that with Facebook. It can be location data from images. In theory it could also be things like "you messaged a person who leans towards a particular political side". All is data that can be data mined and used to calculate the highest revenue advertisement at any specific time you load a Facebook page.

Two high profit questions that historically advertisement networks want to find out is when someone is expecting children, and when they are most likely to go to Disneyland.