Every registered domain has at least two Name Server records which show where it's hosted i.e. by using these records you direct your domain to the servers of a specific hosting company. This way, you have got both your website and your emails managed by the same company. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, for instance A and MX. The former shows which server deals with the website for a given domain address and is always an IP address (18.104.22.168), while the second one reveals which server handles the emails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you enter a domain in your browser, your request is sent through the global DNS system to the provider whose NS records the domain name uses and from there you may be directed to the servers of another service provider provided you have set an IP address of the latter as an A record for your domain address. 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 would like.