Each registered domain name has no less than 2 Name Server records which show where it's hosted i.e. by using these records you point your domain name to the servers of a certain website hosting company. That way, you have got both your website and your e-mails handled by the exact same company. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, such as A and MX. The former shows which server deals with the website for a given Internet domain and is always an IP address (123.123.123.123), while the latter reveals which server manages the emails and is always an alphanumeric string (mx1.domain.com). For example, any time you enter a domain name in your web browser, your request is forwarded through the global DNS system to the provider whose NS records the domain address uses and from there you may be forwarded to the servers of a different company provided you have set an IP address of the latter as an A record for your domain. Having separate records for the site and the e-mails suggests that you can have your site and your e-mails with 2 different providers if you wish.