A subdomain is a website address, that's under a main, or a root domain name. One example 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 site and records i.e. apart from using the domain name as part of the whole web address, a subdomain can be completely independent and even hosted by a separate company. Employing a subdomain can be extremely beneficial if you want to have different web sites which are associated in some way. For instance, you could have an on-line store under the main domain along with a forum under a subdomain so as to supply means for your customers to ask questions and / or share thoughts concerning your products. The advantage of employing a subdomain instead of a subfolder is that the web sites will be separated, so you can update one of them or perform maintenance not affecting the other.