Domain Registrars

Domain name registrar is a company that for all intensive purposes has a license to offer a domain registration service for end users. Domain name registrars buy domain names directly from Domain Name Registries and are also accredited by the Internet Corporation for Assigned Names and Numbers (ICANN) or by a country code top-level domain (ccTLD) authority.

ICANN oversees the most common domain name extensions, including .com,
.net, .biz, and many others. ICANN works with many registries
worldwide, while others are independent of ICANN.

Some Word Wide Registriers include:
Verisign – manages .com, .net, .name
Afilias – manages .info
NeuStar – manages .biz and .us
PIR – manages .org
auDA – manages .au domains
Nominet – manages .uk domains
CIRA – manages .ca domains
DENIC – manages .de domains

Some well know Domain Name Registrars include:
Network Solutions