Top Level Domains (TLDs) are the second highest level in the Domain Name System (DNS); a naming system for Internet resources. The hierarchy of the Domain Name System (DNS) is as follows: root zone > top level domains > second level domains. The root zone is managed by IANA with oversight from ICANN. The root zone is name-less but includes information about the Top Level Domains. The Top Level Domains are created by ICANN and ICANN assign an organisation to administrate the Top Level Domain. The organisation who administrates the Top Level Domain operates a registry (database) for the domain and, if the Top Level Domain is unrestricted, allowed registrants (companies, individuals) to register Second Level Domains in it. The operator of a TLD maintains the master batabase for the zone and also publishes a zone file for the domain. For example, the google.info domain name: the organisation who operates the info Top Level Domain is Afilias Limited.
There are currently over 1000 Top Level Domains in the Root Zone. Generally speaking, each Top Level Domain is managed by a different organisations, although some organisations manage multiple Top Level Domains; such as Versign, who manage the com and net Top Level Domains. The full list of the organisations who manage Top Level Domains can be found on the IANA website located at the following address: iana.org/domains/root/db. The organisations who manage Top Level Domains changes, these companies sign a contract with ICANN to manage the domain for a set period of time, when this time expires they have to reapply to manage the domain with ICANN. Popular Top Level Domains like com and net are profitable to manage, therefore, many companies desire to manage the registry for these domains. To begin with only five Top Level Domains existed (1985), the amount of TLDs was expanded as the amount of desirable namespace in the original domains was 'filled up'. Listed below, is some examples of TLDs and the companies who manage / operate / administrate them:
The vast majority of new TLDs were created after 2012; when a change in policy was implemented by ICANN. The expansion of TLDs is somewhat controversial: with businesses upset at the extra cost and complexity of having to purchase more TLDs to maintain exclusivity for their business name. Some of the new TLDs are: football, guitars, free, cricket, lol, you, yoga, coach, camera, diet and digital. Some of the new TLDs are named after established companies and are operated by the said companies: audi, barclays, boots, prudential and nike.