With the upcoming migration for Java Edition, there may be some confusion about what Gamertags are and how they differ from Usernames. This article should clear up any confusion about the differences between the two. 

Gamertags are used for Microsoft accounts only. If you view your Microsoft account online, you will see your Gamertag as your account name and not your Minecraft Username. Any purchase information and account settings tied to your Microsoft account will display your Gamertag. You can find your Gamertag by signing into https://www.xbox.com/en-US/ and checking the top right.  

In this example the Gamertag is MCgtag1. 

When playing Minecraft: Java Edition you will see your Username in-game and not your Gamertag. The only time you will see your Minecraft Username is in-game and in your Minecraft account settings. You will still be able to view and change your Minecraft: Java Edition Username as usual on www.minecraft.net. Just navigate to your profile information.  

In this example the Minecraft Username is “mooboom”