Look up the various DNS record types, specifically: A, CNAME
"A" is a standard address record, "CNAME" is a "canonical name" record (i.e., an "alias"). Your server should have one "A" record in DNS, and as many "CNAME" records as you require.
Here is some basic info: http://support.google.com/a/bin/answ...n&answer=48090
. This is talking about Google stuff, but the descriptions of the DNS record types are useful and simple to understand.