The data of the wildcard record are used as default values for answering DNS queries about any name which does not exist in the wildcard record's zone.

Wildcards are most commonly used with MX records to direct mail addressed to nonexistent names in the zone to some specific mail server. For this to work, you must also configure your mail server to accept mail addressed to any name inside your domain.

For example, by creating a name *.namesurfer.com with some suitable MX records, it would be possible to send mail to users at xyzzy.namesurfer.com, foo.bar.namesurfer.com, or any other nonexistent host in the namesurfer.com zone.

Even if you use a wildcard MX record, you still need to add individual MX record to the domain names of all your existing hosts (because wildcard records apply to nonexistent names only).

Wildcards match both single-label names and multiple-labels names. For example, both a.namesurfer.com and b.c.d.e.namesurfer.com would be matched by *.namesurfer.com, if they had no specific records of their own.