Whats the point on restoring purchases?

[nriccar]

Hello to all!

First of all, thanks for reading.

I have this doubt, it could seem naive from my part but I don't really get the point.
If a user subscribes to a auto-renewal subscription, it will get access to X part on my app. We save that information in our DB.

If the same user wants to access that subscription from another device, our app would ask for login, and after it, that subscription would be accessible.

What does it do the restore purchase action itself?

[nriccar]

duplicate of #2415