A subdomain is a web address, which is under a main, or a root domain. One example is something.domain.com, in which domain.com is the main domain, while "something" is the subdomain below it. Every single subdomain can have its own site and records i.e. aside from employing the domain name as a part of the whole web address, a subdomain can be entirely independent and even hosted by a separate service provider. Using a subdomain can be very handy if you wish to have different web sites which are associated in some way. For instance, you can have an on-line store under the main domain plus a forum under a subdomain in order to supply means for your customers to ask questions or share views concerning your products. The benefit of using a subdomain instead of a subfolder is that the web sites will be separated, so that you can update one of them or perform maintenance without affecting the other.