Each registered domain name has at least two Name Server records which show where it is hosted i.e. by using these records you direct your domain address to the servers of a certain web hosting provider. In this way, you have got both your site and your e-mails managed by the very same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there are lots of other records, for instance A and MX. The first one reveals which server deals with the site for a given domain address and is always an IP address (188.8.131.52), while the latter shows which server manages the emails and is always an alphanumeric string (mx1.domain.com). For instance, whenever you type a domain in your browser, your request is forwarded through the global DNS system to the provider whose NS records the domain uses and from there you may be directed to the servers of a different provider if you have set an IP address of the latter as an A record for your domain. Having independent records for the site and the emails means you may have your site and your emails with 2 different providers if you would like.