Acronym for Fully Qualified Domain Name.
A fully qualified domain name consists of a host and domain name, right up to and including the top-level domain (TLD).
www.wlug.org.nz is a FQDN. The HostName is www (an alias to 'hoiho'), the third-level domain (you don't hear this mentioned very often) is wlug; the second-level-domain is org and the top-level domain is .nz.
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