Every registered domain name has no less than 2 Name Server records that show where it is hosted i.e. by using these records you direct your Internet domain to the servers of a particular hosting provider. That way, you have got both your site and your e-mails handled by the same provider. On the lower level of the Domain Name System (DNS), however, there are a number of other records, like A and MX. The former shows which server deals with the website for a given Internet domain and is always an IP address (188.8.131.52), while the latter shows which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). For example, when you enter a domain name in your Internet browser, your request is sent through the global DNS system to the provider whose NS records the domain uses and from there you could be sent to the servers of another service provider in case you have set an IP address of the latter as an A record for your domain address. Having independent records for the site and the emails means you can have your site and your e-mails with 2 different providers if you wish.