A subdomain is a website 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. Each subdomain can have its own website and records i.e. apart from employing the domain name as part of the whole web address, a subdomain can be totally independent and also hosted by a separate service provider. Employing a subdomain can be very useful if you wish to have different websites which are connected in some way. As an example, you may have an on-line store under the main domain along with a forum under a subdomain in order to offer means for your clients to ask questions and share experiences about your products. The advantage of using a subdomain as opposed to a subfolder is that the web sites are going to be separated, so you are able to update one of them or perform maintenance without affecting the other.