Each registered domain name has a minimum of two Name Server records which show where it's hosted i.e. by using these records you direct your domain address to the servers of a specific website hosting company. This way, you have got both your site and your emails handled 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 former reveals which server deals with the website for a given domain address and is always an IP address (18.104.22.168), while the latter indicates which server handles the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, whenever you type a domain address in your web browser, your request is forwarded through the global DNS system to the company whose NS records the domain address uses and from there you will be forwarded 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 different records for the site and the e-mails means that you may have your site and your e-mails with 2 different companies if you wish.