Each registered domain name has a minimum of two Name Server records that show where it's hosted i.e. by using these records you direct your domain to the servers of a specific website hosting provider. This way, you have both your website and your emails handled by the very same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, for example A and MX. The first one reveals which server deals with the website for a given domain address and is always an IP address (123.123.123.123), while the latter shows which server manages the emails and is always an alphanumeric string (mx1.domain.com). As an example, when you enter a domain name in your Internet browser, your request is forwarded through the global DNS system to the provider whose NS records the domain name uses and from there you may be directed to the servers of a different provider provided 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 that you can have your site and your emails with two different providers if you would like.