Isn’t that essentially what DNS is? It may cache results but it has to get the results at some point and they communicate with other DNS servers that have the information?
A recursive resolver starts at the root of the tree and walks downwards. Most OSes only have stub resolvers, which simply forward your request to a given recursive resolver, and don't traverse any tree.
AFAIK it's just a proxy to another DNS server with the added benefit of being able to resolve local domain names through mDNS.
Isn’t that essentially what DNS is? It may cache results but it has to get the results at some point and they communicate with other DNS servers that have the information?
Yes, but systemd-resolved is only a stub resolver, not a real resolver.
A recursive resolver starts at the root of the tree and walks downwards. Most OSes only have stub resolvers, which simply forward your request to a given recursive resolver, and don't traverse any tree.