Top Level Domain (TLD) is the element at the rightmost of a domain name, such as .com, .net or .biz. Recently, new TLDs like .pro or .museum were added to supplement older TLDs. ccTLDs (country code TLDs), like .uk or .fr are used per-country.
Below are some of the common TLDs,
.com was one of the original top-level domains, established in January 1985, and has grown to be the largest TLD in use. Although .com domains have always been intended for commercial use, they are currently available for anyone to register.
.net was one of the original top-level domains, created in January 1985. It was initially intended for use by network oriented entities such as Internet service providers. Currently, there are no formal restrictions on who can register a .net domain name. Therefore, while still popular with network operators, it is often treated as a second .com by many.
.biz is intended for domains to be used by businesses; the name is a phonetic spelling of the first syllable of "business." It was created to relieve some of the demand for the finite domain names available in the .com top-level domain, and to provide an alternative to businesses whose preferred .com domain name had already been registered by another party. There are no specific legal or geographic qualifications to register a .biz domain name, except that it must be for "business or commercial use".
.org was one of the original top-level domains, established in January 1985, originally intended for use by organizations that did not meet the requirements for other TLDs. Now anyone can register a .org domain. .org was the domain commonly recommended for use by individuals, although .name and .info are now alternatives.