Each registered domain has no less than two Name Server records which show where it's hosted i.e. by using these records you direct your domain name to the servers of a particular website hosting company. In this way, you've got both your site and your e-mails managed by the very 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 first one reveals which server manages the website for a given Internet domain and is always an IP address (184.108.40.206), while the second one shows which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you type a domain name in your web browser, your request is directed through the global DNS system to the company whose NS records the domain name uses and from there you may be sent to the servers of a different provider provided you have set an IP address of the latter as an A record for your Internet domain. Having different records for the site and the e-mails means that you may have your site and your e-mails with two different companies if you'd like.