Why do Xbox gamertags sometimes have stuff like [GOAT] in front of them?
The Xbox gamertags sometimes have stuff like [GOAT] in front of them symbolizing a clan. Clans are important to your gamertag, you could name yourself after the clan you're in like this: [clanname] Shadow, or [clanname] Ghost.
That usually indicates the "clan" or group of friends that the player is with. Although some games have "clantag" support, many don't, so with some more serious gamers will stick with their clans.
This is referring to a Clan, team, Guild or Group of people they play with. Its simply a clan tag put there because games don't often have the option to have your teams name