Facebook tries to clarify how it collects data when you're not on Facebook
Facebook outlined its data collection practices. According to Product Management Director David Baser, some third-party websites and apps send data about their users to Facebook, regardless of whether those users have Facebook profiles. In return for that information, Facebook helps those websites serve up relevant ads or receive analytics that help them understand how people use their services. The company gets this data from websites and apps that let people share or like posts using Facebook plugins, or log into the website with their Facebook accounts.