Domain name registries most common

Though these are general guidelines, you may use any of these extensions when registering a domain name. 

.com represents companies or for profit organizations, it is also the most common extension for domain names. Most personal web sites also use this extension.

.net generally represents Internet Service Providers. But can be companies or for profit organizations, it is also the a  common extension for domain names. Some personal web sites also use this extension.

.org represents non-profit organizations or groups.

.TV This is New ! represents Television or for profit organizations.

.info This is New ! represents information or for profit organizations.

.us This is New !  represents United States or for profit organizations.

.biz This is New !  represents business or for profit organizations.

.ws   represents web site or for profit organizations.

.name This is New ! represents personal web site or for profit organizations.

Domain name registries around the world

The list below contains the two-letter TLDs according to IANAs list, all in alphabetical order. For listing sorted by country names in alphabetical order, please see the alphabetical country-name list. The contents of these lists are identical.

gTLDs a b c d e f g h i j k l m n o p q r s t u v w x y z

NOTE: NORID is only administering the .no TLD

The list below contains the English country name according to IANAs list, all in alphabetical order. The link takes you to the registration authority of the TLD. For listing sorted by country code TLD (ccTLD) in alph abetical order, please see the alphabetical ccTLD list. The contents of these lists are identical.

gTLDs a b c d e f g h i j k l m n o p q r s t u v w x y z

NOTE: Norid is only administering the .no TLD