Each registered domain name has a minimum of two Name Server records that show where it is hosted i.e. by using these records you direct your domain to the servers of a specific hosting company. That way, you have got both your site and your emails managed by the very same company. On the lower level of the Domain Name System (DNS), however, there are a number of other records, such as A and MX. The former shows which server manages the site for a given domain name and is always an IP address (123.123.123.123), while the second one indicates which server manages the emails and is always an alphanumeric string (mx1.domain.com). For instance, when you enter a domain in your web browser, your request is forwarded through the global DNS system to the provider whose NS records the domain name uses and from there you will be forwarded to the servers of another company provided you have set an IP address of the latter as an A record for your Internet domain. Having independent records for the site and the e-mails suggests that you may have your site and your e-mails with two different providers if you wish.