A subdomain is a website address, that is under a main, or a root domain name. An example is something.domain.com, in which domain.com is the main domain name, while "something" is the subdomain below it. Every 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 entirely independent and also hosted by a different provider. Employing a subdomain can be very beneficial if you'd like to have different websites that are associated in some way. For example, you can have a web-based store under the main domain plus a forum under a subdomain in order to offer means for your clients to ask questions and share opinions regarding your products. The main advantage of using a subdomain instead of a subfolder is that the sites will be separated, so you can update one of them or perform maintenance without affecting the other.