A subdomain is a web address, that is under a main, or a root domain name. An illustration is something.domain.com, in which domain.com is the main domain name, while "something" is the subdomain below it. Every single subdomain can have its own website and records i.e. apart from employing the domain name as part of the whole web address, a subdomain can be totally independent and also hosted by a separate provider. Using a subdomain could be very practical if you wish to have different sites that are associated in some way. For example, you could have an online store under the main domain plus a forum under a subdomain so as to supply means for your customers to ask questions and share views concerning your products. The main advantage of employing a subdomain as opposed to a subfolder is that the web sites are going to be separated, so you're able to update one of them or perform maintenance not affecting the other.