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, while "something" is the subdomain below it. Each and every subdomain can have its own website and records i.e. aside from employing the domain name as part of the whole web address, a subdomain can be completely independent and also hosted by a separate provider. Using a subdomain can be quite practical if you'd like to have different web sites which are related in some way. As an example, you may have an on-line store under the main domain plus a forum under a subdomain so as to provide means for your customers to ask questions and / or share views about your products. The benefit of using a subdomain as opposed to a subfolder is that the web sites are going to be separated, so that you can update one of them or perform maintenance without affecting the other.