Every registered domain name has at least two Name Server records that show where it is hosted i.e. by using these records you point your domain to the servers of a certain web hosting company. This way, you've got both your website and your emails managed by the exact same provider. On the lower level of the Domain Name System (DNS), nevertheless, there are a number of other records, like A and MX. The first one reveals which server handles the site for a given domain name and is always an IP address (18.104.22.168), while the second one indicates which server handles the e-mails and is always an alphanumeric string (mx1.domain.com). As an example, any time you type a domain in your Internet browser, your request is sent through the global DNS system to the provider whose NS records the domain name uses and from there you may be forwarded 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 separate records for the website and the e-mails suggests that you can have your website and your emails with 2 different providers if you would like.