Its an authoritative DNS service, so it can host your domains.

Compare with a recursive resolver, like 8.8.8.8 or 1.1.1.1, which you can use to resolve domains.

What's nice about Bunny DNS is that they have authoritative nameservers ~everywhere, so resolving is quick everywhere.

But I think in practice this isn't that useful, since if a domain is moderately used, its DNS records will be cached ~everywhere in anycasted recursive resolvers.