You will need a Microsoft Account to take advantage of most of the services that Xbox provides – purchasing content from the Xbox Store, connecting with friends, gaming online, using cloud saves and more. Signing up for a Microsoft account and using it on your console allows you to access Xbox Live, which means you can start earning achievements while playing games too.
A Microsoft Account comprises Xbox plus other Microsoft products – Windows, Office, Outlook, Skype and more. If you already have a Microsoft account that you use for logging into Windows or Skype, we recommend that you use the same account for Xbox that you use for everything else. This is because Xbox is more than just the console these days; there are Xbox enabled games on mobile, on PC, even a couple on Nintendo Switch. To keep all of your purchases, your friends and your achievements together, it's best to stick to one account.