Virtual Domain. A website setting on its own domain name. For example this web
site is located on the Virtual Domain www.searchengineworld.com. ...
www.webmasterworld.com/glossary/virtual_domain.htm

apartados in this case reffers to "domain names"


Controlled by the world-wide orgainzation called ICANN, domain names are obtained on a first-come basis, and are used to identify your unique web site (For instance, www:yourname.com.) Most common are the suffixes: .com, .org, and .net. However there are a large number of new suffixes giving a lot more name options. A top level domain can be obtained by paying an annual registration fee to a domain registrar such as Register.com. Fees range from under $10 a year to $30 a year. Some web hosting providers such as iPowerweb.com offer a domain name as part of the monthly hosting fee.
http://www.100best-free-web-space.com/glossary15.html




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Note added at 54 mins (2006-02-28 14:46:53 GMT)
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Postfix - Hosting Multiple Domains with Virtual AccountsEach virtual domain can host services such as web sites and email as if it were the only domain ... For this configuration, list each virtual domain in the ...
www.akadia.com/services/postfix_separate_mailboxes.html

I highly recommend this link for it explains very well this 'domain' concept: http://www.akadia.com/services/postfix_separate_mailboxes.ht...