Gray border around my mac screen

There is a translucent gray border around my mac screen that randomly appeared. It makes it very difficult to move things around and also blocks the close, minimize, and expand buttons. Can I make this go away?

Could you please tell how you fixed it?

My baby kid turned this on by randomly pressing the keys

Solution:

The problem is that the expose window is stuck.  In order to force a refresh take these steps. 1. launch terminal 2. type killall Dock

For those unfamiliar with terminal, or how to launch it, do this:

type command + spacebar to open your search. Type "terminal" in the search and then "enter" to launch terminal.

You'll see a screen with a blinking cursor. Type:

killall Dock

Hit enter.