A subdomain is a web address, that is under a main, or a root domain. One example is something.domain.com, in which domain.com is the main domain address, while "something" is the subdomain below it. Each and every 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 totally independent and also hosted by a different company. Employing a subdomain could be very handy if you want to have different web sites which are associated in some way. For instance, you can have a web-based store under the main domain as well as a forum under a subdomain in order to offer means for your customers to ask questions and share experiences concerning your products. The best thing about employing a subdomain rather than a subfolder is that the sites are going to be separated, so you can update one of them or perform maintenance without affecting the other.