Checking In and Out
The checked in/out icon, represented by a light bulb, reflects the state of a page or file.
Once you begin editing a page (by clicking the edit button), that file is checked out to you and the light bulb is turned ON. Similarly, if you click on the light bulb at the top of the page - or in the filename's row while in Pages view - and turn it on, that page is checked out to you.
You need to check out a page in order to edit the Page Properties.
When a page or file is checked out to a user, no other users can make changes until the file has been checked back in. If you make changes to a file and save those changes, the file is still checked out to you, until you either manually check it in by clicking the light bulb off, or when you publish the file.
When the user publishes a page it is automatically checked back in.
A user might also decide to check out a page in order to make other page options available, in Properties.
OU Campus also has status indicators help make clear why a page is not available for editing as well as who has checked out a page, scheduled an action, or if the page is in the process of a workflow. These icons are shown on many of the screens that display content lists, most notably the File Navigation sidebar, Pages list view and the My Checked-Out Content gadget. (See the diagram below)
Best practice is to make sure to check the page back in when finished editing the page so it can be made available to other users. REMEMBER, when you publish a file, it automatically is checked back in.