When the Domain Name System was devised in the 1980s, the domain name space was divided into two main groups of domains. The country code top-level domains (ccTLD) were primarily based on the two-character territory codes of ISO-3166 country abbreviations. In addition, a group of seven generic top-level domains (gTLD) was implemented which represented a set of categories of names and multi-organizations. These were the domains gov, edu, com, mil, org, net, and int.
During the growth of the Internet, it became desirable to create additional generic top-level domains. As of October 2009, 21 generic top-level domains and 250 two-letter country-code top-level domains existed. In addition, the ARPA domain serves technical purposes in the infrastructure of the Domain Name System.
During the 32nd International Public ICANN Meeting in Paris in 2008, ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains." This program envisions the availability of many new or already proposed domains, as well as a new application and implementation process. Observers believed that the new rules could result in hundreds of new top-level domains to be registered. In 2012, the program commenced, and received 1930 applications. By 2016, the milestone of 1000 live gTLD was reached.
The Internet Assigned Numbers Authority (IANA) maintains an annotated list of top-level domains in the DNS root zone database.
For special purposes, such as network testing, documentation, and other applications, IANA also reserves a set of special-use domain names. This list contains domain names such as example, local, localhost, and test. Other top-level domain names containing trade marks are registered for corporate use. Cases include brands such as BMW, Google, and Canon.