AT&T Protect Advantage

Good Morning!

I have 9 lines total on my account. 4 of them are cell phones. On one of the lines, I have noticed an  AT&T Protect Advantage for 4 that cost $40.00/mo. How does this work? Does this mean I don't need to have a separate protection plan for each phone? How do I go about using this plan on other devices besides the one that it is connected to?

Thank you for your help.