A subdomain is a web address, which is under a main, or a root domain name. An example is something.domain.com, where domain.com is the main domain, while "something" is the subdomain below it. Each and every subdomain can have its own site and records i.e. apart from using the domain name as a part of the whole web address, a subdomain can be entirely independent and even hosted by a different provider. Using a subdomain could be very beneficial if you wish to have different web sites which are related in some way. For instance, you may have a web-based store under the main domain along with a forum under a subdomain so as to supply means for your customers to ask questions or share thoughts about your products. The best thing about employing a subdomain as opposed to a subfolder is that the sites are going to be separated, so you are able to update one of them or perform maintenance without affecting the other.