Every registered domain name has a minimum of two Name Server records that show where it is hosted i.e. by using these records you point your domain name to the servers of a particular hosting company. This way, you have got both your website and your e-mails managed by the exact same company. On the lower level of the Domain Name System (DNS), on the other hand, there are lots of other records, for example A and MX. The former reveals which server deals with the website for a given domain address and is always an IP address (18.104.22.168), while the latter shows which server handles the e-mails and is always an alphanumeric string (mx1.domain.com). For example, any time you enter a domain in your web browser, your request is directed through the global DNS system to the provider whose NS records the domain uses and from there you may be directed to the servers of a different provider provided you have set an IP address of the latter as an A record for your domain name. Having different records for the site and the emails means you may have your website and your e-mails with two different companies if you wish.