A subdomain is a website url, that's 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. Each and 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 entirely independent and even hosted by a different service provider. Using a subdomain could be very practical if you'd like to have different web sites that are related in some way. For instance, you can have a web-based store under the main domain and a forum under a subdomain in order to supply means for your customers to ask questions and share thoughts concerning your products. The benefit of employing a subdomain rather than 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.