A subdomain is a website url, that is under a main, or a root domain. An example is something.domain.com, where domain.com is the main domain name, while "something" is the subdomain below it. Every single subdomain can have its own website and records i.e. apart from employing the domain name as a part of the whole web address, a subdomain can be completely independent and also hosted by a separate service provider. Employing a subdomain can be extremely practical if you want to have different web sites which are associated in some way. For example, you may have an on-line store under the main domain plus a forum under a subdomain in order to offer means for your customers to ask questions and share opinions concerning your products. The best thing about using a subdomain as opposed to a subfolder is that the web sites will be separated, so that you can update one of them or perform maintenance without affecting the other.