It should come as no surprise to you that Facebook collects data on what you like, etc. You already know this because you see ads pop up on Facebook that seem oddly specific to your own personal tastes. Well, get ready for those to start showing up all over the Internet.
Google already uses data to help target advertising and does this externally through Adsense. Facebook has targeted ads on Facebook, for which it uses the enormous amount of personal data it collects from its very purpose (i.e. people create profiles about themselves to share, and those profiles provide the data needed for targeted ads). It's a goldmine, and Facebook has officially announced the gold rush.
Facebook's advertising matrix will be taken outside of the website itself and be placed on various external websites. There's no word yet as to which websites these will be, but Facebook owns quite a few pretty popular ones, such as the ubiquitous Instagram.
Partnering with Facebook for access to this wealth of information could become increasing popular in coming months, which wouldn't be such a bad thing for the company, considering its struggles answering to Wall Street.