Board Thread:Support Requests - Getting Technical/@comment-32935159-20171107031839/@comment-24253265-20171107061621

Simplified, if you protect your main page folks can still edit templates used on the main page, or overwrite files used on the main page with new uploads. With a cascading protection the templates and files used on your main page are automatically protected while they are used on the main page.

Like all protections this is quite annoying for all users trying to improve a template or file, and cascading protections can be rather obscure, if a perfectly harmless unprotected template or unprotected file ends up as protected just because it happens to be used on a protected page with cascading protection.

OTOH if your wiki has some determined vandals or spammers you might need this. Special:ListGroupRights mentions a protect right, apparently you have that, and also mentions a protectsite right, and maybe that's what you don't have for the cascading business.