Every registered domain name has no less than 2 Name Server records that show where it is hosted i.e. by using these records you point your domain address to the servers of a particular web hosting company. That way, you've got both your site and your emails managed by the very same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, like A and MX. The former shows which server handles the site for a given Internet domain and is always an IP address (220.127.116.11), while the second one shows which server handles the emails and is always an alphanumeric string (mx1.domain.com). For example, when you type a domain name 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 may be directed to the servers of another provider if you have set an IP address of the latter as an A record for your Internet domain. Having different records for the website and the emails means that you can have your website and your e-mails with 2 different providers if you wish.