A subdomain is a web address, 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 site and records i.e. aside 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. Employing a subdomain can be very practical if you wish to have different web sites that are connected in some way. For example, you can have a web-based store under the main domain and a forum under a subdomain so as to provide means for your clients to ask questions or share experiences regarding your products. The main advantage of using a subdomain as opposed to a subfolder is that the web sites are going to be separated, so you are able to update one of them or perform maintenance without affecting the other.