A subdomain is a web address, that is under a main, or a root domain name. An 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. apart from using the domain name as part of the whole web address, a subdomain can be entirely independent and also hosted by a separate service provider. Employing a subdomain can be extremely handy if you wish to have different sites which are connected 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 offer means for your customers to ask questions and share experiences regarding your products. The advantage of using a subdomain instead of a subfolder is that the web sites will be separated, so you're able to update one of them or perform maintenance without affecting the other.