Malware is spreading on the Facebook platform posing as emails from Facebook saying you have been tagged in a photo. Clicking on the link will redirect you to a malware download site, and then almost immediately to Facebook, so you may not even know that this has happened. Please be careful opening these emails. It is usually a better course of action to simply go to your Facebook page and search for the photo tag there. Of course, in this case, you would not find one, and that would indicate that the email was fake.