A subdomain is a website address, which is under a main, or a root domain name. An illustration is something.domain.com, where domain.com is the main domain name, while "something" is the subdomain below it. Each subdomain can have its own website and records i.e. apart from using the domain name as a part of the whole web address, a subdomain can be completely independent and even hosted by a different provider. Employing a subdomain can be very beneficial if you wish to have different websites which are connected in some way. For instance, you could have an on-line store under the main domain as well as a forum under a subdomain in order to provide 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 without affecting the other.