Every registered domain has at least two Name Server records which show where it is hosted i.e. by using these records you point your domain address to the servers of a particular hosting company. In this way, you have both your website and your emails handled by the very same company. On the lower level of the Domain Name System (DNS), however, there is a variety of other records, like A and MX. The first one shows which server handles the site for a given Internet domain and is always an IP address (18.104.22.168), while the latter shows which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you enter a domain in your Internet browser, your request is forwarded through the global DNS system to the company whose NS records the domain uses and from there you will be directed to the servers of another service provider if 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 e-mails suggests that you can have your website and your e-mails with two different providers if you'd like.