This is the "backstage" or cloud page.

From Woody Leonhard:

Click File, then Options; at the bottom of the General section, uncheck the box next to Show the Start screen when this application starts. Restart the application; you’ll never see the Start screen again.

While you are at it, you may want to check the box marked “Don’t show the backstage when opening or saving files.”

https://windowssecrets.com/top-story...h-office-2013/