A subdomain is a website url, which is under a main, or a root domain name. An illustration is something.domain.com, in which 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 part of the whole web address, a subdomain can be fully independent and even hosted by a different service provider. Using a subdomain can be extremely practical if you wish to have different web sites which are associated in some way. For instance, you can have an online store under the main domain along with a forum under a subdomain in order to offer means for your customers to ask questions and share experiences concerning your products. The benefit of using a subdomain rather than a subfolder is that the web sites will be separated, so you are able to update one of them or perform maintenance not affecting the other.