When an admin clicks on your username they see your profile like anybody else does, but they also see what make and model of phone you are using, also what network you are on, or what browser you are using if you are on a pc.. They also see your IP number and your email address... It sometimes takes a bit of guesswork but by comparing users details they can often tell which users are using which usernames... . . This is mainly used for finding banned users that are using a different Id to reply in chatrooms or forums...