Gamertag
From Xboxic
The Gamertag is your online alias, identifying you to the Xbox Live system and other online players. It's what gamers see when you join their game, and what shows up in your Gamercard as unique nickname. The Gamertag is unique on Xbox Live.
Should you ever want to change your tag, this is possible via Xbox Live Marketplace at a small cost to discourage easy switching after people got a bad reputation on their current nick.
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