Each registered domain name has no less than 2 Name Server records which show where it is hosted i.e. by using these records you point your domain address to the servers of a particular website hosting provider. This way, you have got both your website and your emails handled by the exact same company. 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 reveals which server deals with the website for a given domain address and is always an IP address (123.123.123.123), while the latter indicates which server manages the emails and is always an alphanumeric string (mx1.domain.com). For instance, any time you enter a domain name in your browser, your request is sent through the global DNS system to the provider whose NS records the domain uses and from there you will be forwarded to the servers of a different provider if you have set an IP address of the latter as an A record for your domain address. Having different records for the website and the e-mails suggests that you could have your site and your emails with 2 different companies if you wish.