A subdomain is a web address, that is under a main, or a root domain name. An example is something.domain.com, where domain.com is the main domain, while "something" is the subdomain below it. Each and every subdomain can have its own website and records i.e. aside from using the domain name as part of the whole web address, a subdomain can be completely independent and also hosted by a different provider. Employing a subdomain could be very practical if you wish to have different sites that are related in some way. For instance, you may have an on-line store under the main domain as well as a forum under a subdomain in order to offer means for your clients to ask questions and share opinions about your products. The advantage of using a subdomain rather than a subfolder is that the sites will be separated, so you can update one of them or perform maintenance not affecting the other.