Each registered domain has at least 2 Name Server records which show where it's hosted i.e. by using these records you point your domain address to the servers of a certain web hosting company. This way, you have got both your website and your emails managed by the same provider. On the lower level of the Domain Name System (DNS), however, there are a number of other records, for instance A and MX. The former shows which server handles the website for a given Internet domain and is always an IP address (123.123.123.123), while the latter indicates which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you enter a domain address in your Internet browser, your request is forwarded through the global DNS system to the company whose NS records the domain name uses and from there you will be directed to the servers of another service provider provided you have set an IP address of the latter as an A record for your domain name. Having separate records for the website and the e-mails suggests that you can have your website and your emails with two different companies if you would like.