A domain, or domain name, refers to the name or label used which indicates an area of control on the Internet. Domain names are determined by the Domain Name System, otherwise known as DNS. Hostnames, on the other hand, are connected to an IP address

Top-level domain names, such as COM, ORG, NET, or INFO, among others, comprise the first level of domain names. Country code domains are also considered as part of this category. Second and third-level domain names are taken by users who intend to build websites or connect their local networks to the Internet. The top-level domains start on the right, and the levels go down as one moves to the left. The name on the left is a subdomain of that on its right.

Domain names are useful in attracting visitors to a website. For instance, commonly used search words are often considered as good targets for domain name speculation. Domainers can acquire them at a low price and try to resell them at profit as the demand increases.
Registrants can also engage in domain tasting, by taking advantage of the five-day grace period for domain registration. During this period, the registrant can test the marketability of the name, as well as get an idea of how much income can be made from advertising on a site with the name being tested.