What’s messages?

on the app in the Notification screen you have Alerts and Messages. What, or should I say how do the Messages work? Also, what is the little “file” icon in the upper left?

I’m unsure what Messages is (I don’t have anything there)

The pencil & square button in the upper left of the Notifications tab is to allow you to select multiple Alert videos to delete them at once.

Update: Looks like messages is (at least) used to notify people of cameras shared with them.