Each registered domain name has no less than 2 Name Server records that show where it's hosted i.e. by using these records you point your Internet domain to the servers of a specific website hosting company. In this way, you have got both your site and your emails handled by the very same provider. On the lower level of the Domain Name System (DNS), on the other hand, there is a variety of other records, such as A and MX. The first one shows which server deals with the site for a given Internet domain and is always an IP address (188.8.131.52), while the second one reveals which server manages the emails and is always an alphanumeric string (mx1.domain.com). As an example, whenever you enter a domain in your Internet browser, your request is forwarded through the global DNS system to the provider whose NS records the domain uses and from there you could be forwarded to the servers of another service provider in case you have set an IP address of the latter as an A record for your domain address. Having separate records for the website and the e-mails suggests that you could have your website and your emails with 2 different providers if you would like.