What is a Subdomain?

A subdomain is a domain that is part of a larger domain; the only domain that is not also a subdomain is the top domain.

For example, http://gallery.ctie.org.uk and http://book2.ctie.org.uk are subdomains of the http://www.ctie.org.uk, which in turn is top-level domain (TLD) for the CTiE site

The Domain Name System (DNS) has a tree structure or hierarchy, with each non-RR (resource record) node on the tree being a domain name.

A subdomain is a domain that is part of a larger domain; the only domain that is not also a subdomain is the top domain.

Specific to the CTiE site the subdomains (five on Cloud7) can be considered as separate sites with only a link, hence in the future these can be isolated without affecting the main site. These are in fact separate stores of past events worth recording.