From a UI point a name is a way for humans to identify a thing. So a username is just a way to identify a user, if multiple users have the same username you can

From a UI point a name is a way for humans to identify a thing. So a username is just a way to identify a user, if multiple users have the same username you cant identify which one. Starcraft allows people to have the same username, tell your mate your username and ask him to add you, he wont be able to. You need to go through settings and find your unique user pin which you cant remember, then give that too your mate, they need both. Use email and a screen name, your mate already knows your username and can add you, you can call yourself whatever you want.