Every registered domain has a minimum of two Name Server records that show where it's hosted i.e. by using these records you direct your Internet domain to the servers of a certain hosting provider. In this way, you have both your website and your e-mails managed by the very same provider. On the lower level of the Domain Name System (DNS), nevertheless, there are lots of other records, such as A and MX. The former shows which server handles the site for a given domain and is always an IP address (220.127.116.11), while the second one reveals which server handles the emails and is always an alphanumeric string (mx1.domain.com). As an example, when you type a domain in your Internet browser, your request is forwarded through the global DNS system to the provider whose NS records the domain uses and from there you could be forwarded to the servers of a different provider provided you have set an IP address of the latter as an A record for your domain. Having different records for the site and the emails means that you could have your website and your e-mails with two different providers if you'd like.