A subdomain is a website url, that is under a main, or a root domain. An example is something.domain.com, in which 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 part of the whole web address, a subdomain can be completely independent and also hosted by a separate provider. Employing a subdomain can be quite practical if you want to have different sites that are related in some way. For instance, you could have an on-line store under the main domain and a forum under a subdomain so as to offer means for your customers to ask questions and / or share thoughts concerning your products. The benefit of using a subdomain as opposed to a subfolder is that the sites will be separated, so you are able to update one of them or perform maintenance without affecting the other.