Every registered domain has a minimum of 2 Name Server records which show where it is hosted i.e. by using these records you point your domain name to the servers of a particular hosting company. In this way, you've got both your site and your emails managed by the exact same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there are lots of other records, for instance A and MX. The former shows which server deals with the site for a given domain and is always an IP address (184.108.40.206), while the latter indicates which server manages the emails and is always an alphanumeric string (mx1.domain.com). As an illustration, whenever you enter a domain name in your web browser, your request is sent through the global DNS system to the company whose NS records the domain address uses and from there you will be sent to the servers of a different service provider in case you have set an IP address of the latter as an A record for your domain address. Having independent records for the site and the emails suggests that you can have your site and your e-mails with 2 different providers if you would like.