Unknown "Sharing and Permissions" Panel Just Popped Up?

So I've had my MBP for 2 years, and I just got a "Sharing and Permissions" Panel in the "Get Info" pane. (right/secondary click on an image > Get Info). I've never seen this panel before. Ever. What is it and why is it htere? Who is "everyone" and "staff"? Here's an attached image: