Every single registered domain has a minimum of 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 certain website hosting provider. This way, you have both your website and your emails handled by the same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there are a number of other records, for example A and MX. The former shows which server deals with the site for a given domain address and is always an IP address (184.108.40.206), while the second one indicates which server manages the emails and is always an alphanumeric string (mx1.domain.com). For instance, any time you enter a domain in your Internet browser, your request is sent through the global DNS system to the company whose NS records the domain uses and from there you will be forwarded to the servers of a different provider provided you have set an IP address of the latter as an A record for your domain. Having different records for the site and the emails suggests that you could have your website and your emails with two different companies if you wish.