A subdomain is a web address, that's under a main, or a root domain. An illustration is something.domain.com, where domain.com is the main domain name, while "something" is the subdomain below it. Each and every subdomain can have its own website and records i.e. apart from employing the domain name as a part of the whole web address, a subdomain can be fully independent and also hosted by a different service provider. Employing a subdomain could be very practical if you want to have different sites that are related in some way. For example, you may have an on-line store under the main domain as well as a forum under a subdomain so as to provide means for your customers to ask questions and share views regarding your products. The benefit of using a subdomain rather than a subfolder is that the websites will be separated, so that you can update one of them or perform maintenance not affecting the other.