Each registered domain name has no less than two Name Server records that show where it's hosted i.e. by using these records you direct your Internet domain to the servers of a particular web hosting provider. This way, you've got both your website and your e-mails managed by the same company. On the lower level of the Domain Name System (DNS), nevertheless, there are lots of other records, such as A and MX. The former reveals which server handles the site for a given domain address and is always an IP address (18.104.22.168), while the second one reveals which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). For instance, any time you enter a domain address in your browser, your request is forwarded through the global DNS system to the company whose NS records the domain uses and from there you could be forwarded 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 separate records for the site and the emails suggests that you can have your website and your emails with two different providers if you wish.