A subdomain is a web address, which is under a main, or a root domain name. One example is something.domain.com, where domain.com is the main domain address, while "something" is the subdomain below it. Every single subdomain can have its own site and records i.e. apart from employing the domain name as a part of the whole web address, a subdomain can be totally independent and even hosted by a separate provider. Using a subdomain can be extremely practical if you wish to have different sites that are related in some way. As an example, you may have a web-based store under the main domain along with a forum under a subdomain so as to provide means for your clients to ask questions and share experiences about your products. The benefit of employing a subdomain instead of a subfolder is that the websites will be separated, so you are able to update one of them or perform maintenance not affecting the other.