Each registered domain has at least 2 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 specific website hosting provider. In this way, you've got both your site and your e-mails managed by the same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there are lots of other records, such as A and MX. The former reveals which server handles the site for a given domain and is always an IP address (184.108.40.206), while the second one reveals which server handles the emails and is always an alphanumeric string (mx1.domain.com). As an illustration, any time you type a domain name in your browser, your request is forwarded through the global DNS system to the provider whose NS records the domain address uses and from there you could be directed to the servers of another provider in case you have set an IP address of the latter as an A record for your domain name. Having independent records for the website and the emails suggests that you can have your site and your emails with 2 different providers if you'd like.