Every single registered domain name has no less than two Name Server records which show where it is hosted i.e. by using these records you point your domain name to the servers of a certain web hosting provider. This way, you have got both your website and your e-mails handled by the very same provider. On the lower level of the Domain Name System (DNS), on the other hand, there are a number of other records, for instance A and MX. The former reveals which server deals with the website for a given domain and is always an IP address (18.104.22.168), while the latter shows which server manages the e-mails 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 forwarded through the global DNS system to the provider whose NS records the domain name uses and from there you could be sent to the servers of a different service provider if you have set an IP address of the latter as an A record for your domain. Having different records for the website and the e-mails means you may have your website and your emails with 2 different providers if you wish.