.com

The domain name com is a generic top-level domain (gTLD) in the Domain Name System of the Internet. Its name is derived fromcommercial, indicating its original intended purpose for networks of general commercial character.

The gTLD com was originally administered by the United States Department of Defense, but is today operated by VeriSign. Registrations incom are processed via registrars accredited by ICANN. The registry accepts internationalized domain names.

.net

The domain name net is a generic top-level domain (gTLD) used in the Domain Name System of the Internet. The name is derived fromnetwork, indicating its originally intended purpose for organizations involved in networking technologies, such as Internet service providers and other infrastructure companies. However, restrictions were never enforced and the domain is a general purpose name space. It is still popular with network operators, and is often treated as an alternate  to com.

The domain name info is a generic top-level domain (gTLD) in the Domain Name System (DNS) of the Internet, The name is derived frominformation indicating that the domain is intended for informative Internet resources, although registration requirements do not prescribe any theme orientation.
The info domain has been the most successful of the seven new domain names, with over 5.2 million domain names in the registry as of April 2008.
Info is an unrestricted domain, meaning that anyone can obtain a second-level domain under info for any purpose, similar to the com,net or org domains.

.org

The domain name org is a generic top-level domain (gTLD) of the Domain Name System (DNS) used in the Internet. The name is derived from organization.

The org domain was one of the original top-level domains, with com, edu, gov, mil and net, established in January 1985. It was originally intended for non-profit organizations or organizations of a non-commercial character that did not meet the requirements for other gTLDs.   

Registrations in the org are processed via accredited registrars worldwide. Anyone can register an org second-level domain. Although orgwas recommended for non-commercial entities, there are no restrictions to registration. There are many instances of org being used by commercial sites. org was also commonly recommended for use by individuals, although name and info are now alternatives. According to the company's Dashboard (Domain Name) report, the composition of .ORG is diverse, including cultural institutions, associations, sports/teams, religious, civic, open source software (such as Wiki, Drupal, Joomla), schools, environmental initiatives, social/fraternal organizations, health, legal services, clubs and community volunteer groups. There are also cases where companies or organizations have created sites under .ORG for crisis management.