You've probably stumbled upon this researching how to remove the Xbox Game Bar. This gist includes a few different methods you can try. Please note that some of these first options are probably not be available unless you are running an older version of Windows 10.
EDIT: make sure to check out the comment below from @nmhung1985 which seems to be working for most folks.
(this is no longer an option on any recent Windows 10 build)
- Press Windows Key or click on the Start menu.
- Start typing
Xbox
orGame Bar
, until you get the Xbox Game Bar app to appear in the results.