The right-most label in a domain name is referred to as its "top-level domain" (TLD). For example, in the domain name www.example.com, the top-level domain is com
While wiki surfing this Sunday, I came across some fun facts about domain names -
Most TLDs with three or more characters are referred to as "generic" TLDs, or "gTLDs". Currently there are 20 gTLDs out of which 6 (.biz, .com, .info, .name, .net, .org) are open TLDs i.e. any person or entity is permitted to register
Country-code top-level domains (ccTLD) are two letter domains established for countries or territories or their internationalized domain names (IDN ccTLD). With some historical exceptions, the code for any territory is the same as its two-letter ISO 3166 code.
A number of the world's smallest countries have licensed their TLDs for worldwide commercial use. For example, Tuvalu and the Federated States of Micronesia, small island-states in the Pacific, have partnered with VeriSign and FSM Telecommunications respectively, to sell domain names using the .tv and .fm TLDs to television and radio stations.
Vanity ccTLDs are TLDs which are used for various purposes outside their home countries, because of their name. The list of ccTLDs on Wikipedia (incompletely) identifies countries (there are atleast 15) that permit foreign registration.
A domain hack (sometimes known as a domain name hack) is an unconventional domain name that combines domain levels, especially the top-level domain (TLD), to spell out the full "name" or title of the domain.
Some popular domain name hacks are who.is, blo.gs, del.icio.us, cr.yp.to, retou.ch, goo.gl, bit.ly and ow.ly
Also see:
My favorite Developer Cheat-Sheets
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