Each registered domain name has no less than 2 Name Server records that show where it's hosted i.e. by using these records you point your domain to the servers of a specific hosting company. This way, you have both your website and your emails managed by the exact same service provider. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, for example A and MX. The former reveals which server manages the site for a given domain address and is always an IP address (188.8.131.52), while the second one shows which server handles the e-mails and is always an alphanumeric string (mx1.domain.com). For example, any time you enter a domain name in your web browser, your request is forwarded through the global DNS system to the company whose NS records the domain address uses and from there you will be sent to the servers of another service provider if you have set an IP address of the latter as an A record for your Internet domain. Having independent records for the website and the emails means that you may have your site and your e-mails with two different companies if you would like.