A subdomain is a website address, that is under a main, or a root domain. One example is something.domain.com, where domain.com is the main domain, while "something" is the subdomain below it. Every subdomain can have its own website and records i.e. aside from employing the domain name as a part of the whole web address, a subdomain can be fully independent and also hosted by a different provider. Using a subdomain can be quite practical if you'd like to have different web sites that are associated in some way. As an example, you may have a web-based store under the main domain as well as a forum under a subdomain so as to provide means for your customers to ask questions or share views about your products. The main advantage of using a subdomain instead of a subfolder is that the websites will be separated, so that you can update one of them or perform maintenance not affecting the other.