Each registered domain has a minimum of 2 Name Server records which show where it's hosted i.e. by using these records you direct your domain to the servers of a certain web hosting company. In this way, you have got both your site and your e-mails managed by the very same company. On the lower level of the Domain Name System (DNS), however, there are a number of other records, for example A and MX. The first one shows which server manages the site for a given domain and is always an IP address (18.104.22.168), while the second one shows which server deals with the emails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you enter a domain in your Internet browser, your request is directed through the global DNS system to the company whose NS records the domain uses and from there you will be forwarded to the servers of a different company provided you have set an IP address of the latter as an A record for your Internet domain. Having different records for the website and the e-mails means you can have your site and your e-mails with two different companies if you'd like.