Every registered domain name has a minimum of two 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 particular website hosting company. That way, you have both your site and your e-mails handled by the same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, for instance A and MX. The former reveals which server handles the website for a given Internet domain and is always an IP address (220.127.116.11), while the latter indicates which server deals with the emails and is always an alphanumeric string (mx1.domain.com). As an example, any time you type a domain name in your browser, your request is sent through the global DNS system to the company whose NS records the domain name uses and from there you could be forwarded to the servers of another provider provided you have set an IP address of the latter as an A record for your domain address. Having separate records for the website and the e-mails means that you may have your website and your e-mails with two different providers if you'd like.