Tagging Facebook users is a simple way to create more engagement and reach. You can tag friends in photos posted by your Page, and you can tag most people that comment on an update.
Keep in mind that you can’t just tag any Facebook user as a Page, although Facebook users can tag almost any Page regardless of whether they’re a fan or not.
When you really think about this, it kinda reflects how the real world works. For example, it’s perfectly acceptable for me to say I like Dunkin’ Doughnuts. But it would feel very creepy for Dunkin’ Doughnuts to say they like me. Get it?