A subdomain is a website address, that's under a main, or a root domain name. One example is something.domain.com, in which domain.com is the main domain, while "something" is the subdomain below it. Every single subdomain can have its own site and records i.e. apart from using the domain name as part of the whole web address, a subdomain can be totally independent and even hosted by a different service provider. Employing a subdomain could be very practical if you want to have different websites that are associated in some way. For example, you could have a web-based store under the main domain as well as a forum under a subdomain in order to supply means for your clients to ask questions and share views concerning your products. The benefit of employing a subdomain rather than a subfolder is that the websites will be separated, so you're able to update one of them or perform maintenance not affecting the other.