Every registered domain has a minimum of 2 Name Server records that show where it's hosted i.e. by using these records you direct your domain to the servers of a particular website hosting provider. That way, you've got both your website and your emails managed by the very same company. On the lower level of the Domain Name System (DNS), on the other hand, there are a number of other records, such as A and MX. The first one reveals which server deals with the website for a given Internet domain and is always an IP address (18.104.22.168), while the second one reveals which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, when you type a domain in your Internet browser, your request is forwarded through the global DNS system to the company whose NS records the domain address uses and from there you could be sent to the servers of a different service provider provided you have set an IP address of the latter as an A record for your Internet domain. Having independent records for the site and the e-mails suggests that you could have your website and your e-mails with 2 different providers if you would like.