A subdomain is a website address, that is under a main, or a root domain. One example is something.domain.com, where domain.com is the main domain address, while "something" is the subdomain below it. Each 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 fully independent and also hosted by a different service provider. Using a subdomain could be very handy if you wish to have different websites that are related 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 supply means for your customers to ask questions or share experiences regarding your products. The main advantage of using a subdomain as opposed to a subfolder is that the websites will be separated, so you're able to update one of them or perform maintenance without affecting the other.