A subdomain is a web address, which is under a main, or a root domain. An illustration is something.domain.com, where domain.com is the main domain address, while "something" is the subdomain below it. Every subdomain can have its own site and records i.e. aside from using the domain name as a part of the whole web address, a subdomain can be totally independent and also hosted by a separate provider. Employing a subdomain could be very beneficial 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 as well as a forum under a subdomain so as to provide means for your clients to ask questions or share views about your products. The main advantage of employing a subdomain as opposed to 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.