Facebook uses your web logins and Likes, anywhere on the Internet, to track you. When you do this, they deposit a “cookie” tracking file on your computer.

If you’ve previously received a cookie from Facebook because you either have an account or have visited facebook.com, your browser sends us information about this cookie when you visit a site with the “Like” button or another social plugin. We use this cookie information to help show you a personalized experience on that site as well as Facebook, to help maintain and improve our service, and to protect both you and Facebook from malicious activity. We delete or anonymize it within 90 days, and we do not sell it to advertisers or share it without your permission.

In the last sentence, “it” refers to the cookie. They do not sell the cookie file or nor share that cookie file with advertisers.
A cookie is not the valuable data, of course. The cookie is used to track your web site visits – even the specific page you have visited at a web site. Cookies are also used in conjunction with hidden single pixel images and other tricks to track your online behavior.
Note also that every page that offers a Facebook button of any kind is tracking you and you probably need not even log in via that page to be tracked. I am in process of removing Facebook “share”, “like” and “Login” buttons from all my web sites.