A subdomain is a website address, which is under a main, or a root domain. An illustration 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. apart from employing the domain name as part of the whole web address, a subdomain can be entirely independent and also hosted by a different provider. Using a subdomain can be extremely useful if you'd like to have different web sites that are connected 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 offer means for your customers to ask questions and share thoughts regarding your products. The advantage of using a subdomain instead of a subfolder is that the sites are going to be separated, so you can update one of them or perform maintenance not affecting the other.