Each registered domain has at least two Name Server records which show where it's hosted i.e. by using these records you direct your Internet domain to the servers of a certain hosting company. That way, you have got both your website and your emails managed by the very same provider. On the lower level of the Domain Name System (DNS), nevertheless, there are lots of other records, like A and MX. The first one shows which server handles the website for a given domain name 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). As an example, when you type a domain in your Internet browser, your request is directed through the global DNS system to the company whose NS records the domain name uses and from there you will be sent to the servers of a different company in case you have set an IP address of the latter as an A record for your domain name. Having different records for the site and the emails suggests that you can have your site and your emails with 2 different providers if you'd like.