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 website hosting company. In this way, you have got both your site and your emails managed by the same provider. On the lower level of the Domain Name System (DNS), nevertheless, there are a number of other records, for example A and MX. The first one reveals which server manages the website for a given domain address and is always an IP address (18.104.22.168), while the latter shows which server handles the emails and is always an alphanumeric string (mx1.domain.com). For instance, when you enter a domain address in your browser, your request is sent through the global DNS system to the provider whose NS records the domain address uses and from there you will 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 you may have your site and your e-mails with 2 different companies if you wish.