Every registered domain has no less than 2 Name Server records which show where it is hosted i.e. by using these records you direct your Internet domain to the servers of a certain hosting provider. This way, you have got both your site and your emails handled by the same company. On the lower level of the Domain Name System (DNS), however, there is a variety of other records, like A and MX. The former shows which server handles the website for a given domain address and is always an IP address (220.127.116.11), while the second one indicates which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you type a domain in your web browser, your request is directed through the global DNS system to the provider whose NS records the domain address uses and from there you could be directed to the servers of another service provider in case you have set an IP address of the latter as an A record for your domain name. Having independent records for the website and the emails suggests that you may have your site and your e-mails with 2 different providers if you would like.