Definition of Top-level Domain in the Network Encyclopedia.
What is Top-level domain?
A Top-level domain is any domain that is directly under the root domain in the hierarchical Domain Name System (DNS). Top-level domains are few in number and are used to identify broad classes of Internet services. Except for country domains, the various top-level domains currently in existence are listed in the following table. A number of additional top-level domains are yet to be finalized and implemented.
Top-Level Domains
| Domain | Description |
| .com | Commercial businesses and personal domains |
| .edu | Mostly U.S. universities and colleges |
| .org | Nonprofit organizations |
| .net | Networking and telecommunications companies |
| .gov | American government branches and agencies |
| .mil | U.S. military |
In addition to the domains listed in the table, countries as well as states and provinces within countries are identified by two-letter country codes. For example, .uk is the top-level domain for the United Kingdom, .ca is the top-level domain for Canada, and mb.ca is the top-level domain for the province of Manitoba in Canada. Although the .com domain is by far the most popular one today due to the way it is marketed, many businesses are forced to use other domains such as .net or their country domain because of the shortage of commercial top-level domains.
NOTE
A special domain called in-addr.arpa is used for reverse DNS name lookups (resolving a host name given the host’s IP address).
