It shows which websites share your nameservers.
Why is this important? Because it can be used against you far easier than IPs.
Did you know that in the big SEO hosting deindexation years ago, it was nameservers that were used to find SEO sites, not IPs?
Why you ask? There are many reasons:
- IPs can be shared between customers and SEO sites and legitimate sites, nameservers very rarely,
- IPs can change hands often between who uses them and who owns them, nameservers do not,
- IPs are owned by big hosts while nameservers can be created by anyone.
So if you’re hosting with an SEO/PBN hosting provider, make sure the nameservers are not unique to their customers.