A domain extension or TLD ( Top Level Domain ), is defined by the letters that follow the last dot of the domain name.
Domains vary in value based on their extension or TLD. A domain with a .com TLD is usually more valuable then a domain with a .net extension. In certain cases a domain with a ccTLD can be extremely valuable ( mainly where the need for that domain name is centralized ).
There are three types of domain extensions, or TLDs currently in use on the internet.
1. ccTLDs or country code top level domains, are used by countries and dependent territories. They are limited to two letters. Examples of ccTLDs are .us (United States), .de (Germany), .at (Austria), .be (Belgium), .it (Italy), .uk (United Kingdom), .in (India), .jp (Japan) etc. For a complete list of ccTLDs click here. The rules of registration of ccTLDs vary from country to country. For example, Indian ccTLD .in can be registered by anyone from across the globe, while the Andorran ccTLD .ad can only be registered by Andorran residents and organizations.
2. gTLDs or generic top level domains were in theory meant to be used by specific types of organizations.Today, almost all gTLDs can be purchased by anyone – with the exception of .mil and .gov which are restricted to US authorities. Examples of gTLDs are .com, .net, .org, .info, .mobi, .asia etc. For a complete list of gTLDs click here.
3. iTLDs or infrastructure top level domains have a limited use. The only known iTLDs are .root and .arpa.