your screen is being observed
Why does my apply mac book air close periodically and then at the top of the grey bar it says my screen is being observed?
MacBook Air 13″
The reason is that your screen is being observed, and (most likely) your Mac is also being controlled by someone other than you.
That cannot occur without your consent. Refer to Allow a remote computer to access your Mac - Apple Support, and to this passage in particular:
"Allowing remote login to your Mac can make it less secure. See Set up your Mac to be secure."