Blocklists via DNS Query
Spamhaus datasets are traditionally consulted through DNS queries, where the object to be queried (an IP or a domain/hostname) is prepended to a DNSBL domain zone.
This scheme has been in use for decades and is thoroughly supported across the mailserver industry, where it became a standard due to its lightweight nature and ease of implementation, to the point of being formalized in [RFC5782](https://tools.ietf.org/html/rfc5782).
Spamhaus Blocklists via DNS Query is simply an implementation of it, with only minor details distinguishing it from most others.