Domain names are the telephone directory of the Internet, mapping a familiar name to a numeric internet address.  The first step before you can host your Web site is to register a domain name so that visitors can actually identify your site and their browsers may be directed to it.  Although different registrars advertise different prices, and about their security and data-centers, all names are actually registered at central locations for each top level domain such as .com, .net or .biz.  The only difference between registrars is the ease with which you can change the information in a record or move the record to a new registrar.