Every registered domain name has a minimum of 2 Name Server records which show where it is hosted i.e. by using these records you direct your domain to the servers of a particular website hosting provider. That 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, such as 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 second one indicates which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, whenever you type a domain address in your Internet browser, your request is forwarded through the global DNS system to the company whose NS records the domain address uses and from there you may be forwarded to the servers of another company in case you have set an IP address of the latter as an A record for your domain name. Having different records for the site and the e-mails means that you may have your website and your e-mails with two different companies if you would like.