A subdomain is a website url, that's under a main, or a root domain name. One example is something.domain.com, in which domain.com is the main domain, while "something" is the subdomain below it. Each subdomain can have its own website and records i.e. aside 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 very practical if you wish to have different sites that are connected in some way. For example, you can have an on-line store under the main domain as well as a forum under a subdomain in order to supply means for your clients to ask questions and share views regarding your products. The best thing about using a subdomain rather than a subfolder is that the websites are going to be separated, so you are able to update one of them or perform maintenance not affecting the other.