Every registered domain name has no less than two 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. This way, you have got both your website and your emails managed by the exact same company. On the lower level of the Domain Name System (DNS), on the other hand, there are a number of other records, like A and MX. The former shows which server handles the site for a given Internet domain and is always an IP address (123.123.123.123), while the latter indicates which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). For instance, when you type a domain address 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 could be forwarded to the servers of a different service provider if you have set an IP address of the latter as an A record for your domain name. Having different records for the website and the e-mails suggests that you could have your site and your e-mails with two different providers if you would like.