A subdomain is a website url, 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 site and records i.e. apart from employing the domain name as part of the whole web address, a subdomain can be completely independent and also hosted by a different provider. Employing a subdomain can be very handy if you'd like to have different web sites that are associated in some way. For instance, you can have an online store under the main domain along with a forum under a subdomain in order to supply means for your clients to ask questions or share views regarding your products. The advantage of using a subdomain instead of a subfolder is that the websites will be separated, so you can update one of them or perform maintenance without affecting the other.