A subdomain is a web address, that is under a main, or a root domain. An illustration 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 site and records i.e. aside from using the domain name as a part of the whole web address, a subdomain can be fully independent and even hosted by a separate service provider. Employing a subdomain can be very handy if you want to have different websites which are associated in some way. For example, you may have a web-based store under the main domain and a forum under a subdomain so as to supply means for your customers to ask questions and share thoughts regarding your products. The advantage of employing a subdomain rather than a subfolder is that the websites are going to be separated, so you're able to update one of them or perform maintenance without affecting the other.