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