Facebook stirred up privacy concerns when it came out that its "Like" and "Share" buttons appearing all over the web actually report your visits back to Facebook servers.

Now Facebook engineering director Arturo Bejar has shared what personal information the company retains with its tracking cookies, as reported by USA Today.

When you're logged in, Facebook will keep a timestamped list of the URLs you visit and pair it with your name, list of friends, Facebook preferences, email address, IP address, screen resolution, operating system, and browser.

When you're logged out, it captures everything except your name, list of friends, and Facebook preferences. Instead, it uses a unique alphanumeric identifier to track you.

Keep in mind that Facebook isn't tracking your entire browsing history, just your visits to sites with "Like" and "Share" buttons.

Bejar told USA Today that Facebook technically could link your name to your logged-out browsing data, but he "makes it a point not to do this."

Why does Facebook gather all this info and what do they do with it? By keeping so many details, it makes it easier to identify fake accounts and scammers. By keeping track of what users "Like" around the web, Facebook can show people ads that will be the most interesting to them and generate more revenue.

Despite Facebook having the best intentions (or at least saying it does) -- wanting to maintain a high quality user experience and generate ad revenue -- you can see why privacy experts and informed users are concerned.