Limitations
A gamer tag can be u to 15 numbers, letters and characters on the Xbox Live network. You can have up to 32 different gamer tags on an Xbox and eight profiles on each system.
Changing Your Name
You can change your gamer tag on the Xbox Live network through the premium network, but you must first pay 800 Microsoft points every time you want to change it.
Avatars
Gamer tags also include avatars or user pictures to show next to your name. It is sometimes easier to look at an image than it is to look at and read the text. You can take your own personal avatar image with the Xbox camera or purchase avatars from the Microsoft store in bundles.
Controversy
Gamer tags cannot contain controversial or offensive messages; if yours does, you may be asked by Microsoft to change your name in order to play. Users were previously not allowed to mention their sexuality, such as gay or lesbian, but public attention from an openly gay gamer caused a media frenzy and Microsoft removed the rule on gamer tags.