Generic domains.
Generic domains were created by ICANN (the organization that manages domain names worldwide) for the use of the Internet audience and are as follows:
.com (originally for commercial enterprises)
.org (initially for non-profit organizations)
.net (originally for Internet companies)
These three domains are restricted
.edu (exclusively for U.S. educational institutions)
.gov (exclusively for U.S. government institutions)
.thousand (exclusively for U.S. military institutions)
.int (limited to entities within the International Telecommunication Union)
And since 2000,
.biz (for commercial purposes)
.info (for informational purposes)
Unrestricted use
.name (for personal names)
.aero (specifically for the world of aviation)
.museum (for museums only)
.pro (for professionals only)
.coop (for cooperatives only)
Country code domains
Country code domains were created to be used by each country. They are: (.es, .uk, .us, .de, etc.). Country code domains are used by organizations and companies that want to establish themselves on the Internet or who want to protect the identity of their brand or business name in a particular country. Territorial domains have two letters, for example, .es for Spain, .fr for France, etc. There are approximately 230 territorial domains. In Spain, the competent authority to manage the country code domain ".es" is ESNIC, a department of the Public Enterprise Body, Red.es.
A domain name is first level (.com), second level (jdnunez.com), or third level (marcas.jdnunez.com).