Best paractice to make full/partial Jahia backup

What is the "serverPermissions.xml" option in the config wizard when importing from a backup file.

Please use some wording which is self-speaking for non Jahia committers. Moreover this is not resource bundlized.

So at the end we do not know exactly what this option really means (I preusme inserting older config related to Jamon or things like that? What does it exactly cover? Which files? Is it documented somewhere?)