A domain is the name that identifies a web site. Each domain is unique within the Internet. The www.ICANN.org domain belongs to its own page on internet, and no other. A single web server can serve many pages of several domains, but a domain can only have one web server.
Domains normally consist of three parts: the three www, the name of the organization (AGIT or ICANN…) and the type of organization (com).
The last part of a domain name (the extension) is called the “Top Level Domain (TLD)”, and the standards for assigning top level domains are established through an international organization, the Internet Corporation for Assigned Names and Numbers (ICANN), www.icann.org.
There are two types of top level domains (TLDs): generic and country code.
Generic names (gTLDs) were created for the public use of the Internet, and the country code domains (ccTLDs) to be used individually in each one. Generic names can be .com, .org, .net, .info .gov, .mil or .int. Country codes are, for example, .uk, .de, .tr or .fr.