Every single registered domain has at least 2 Name Server records that show where it's hosted i.e. by using these records you direct your Internet domain to the servers of a specific web hosting company. In this way, you've got both your site and your e-mails managed by the very same service provider. On the lower level of the Domain Name System (DNS), however, there are lots of other records, such as A and MX. The first one reveals which server deals with the website for a given domain address and is always an IP address (18.104.22.168), while the second one shows which server deals with the e-mails and is always an alphanumeric string (mx1.domain.com). For example, whenever 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 name uses and from there you will 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 address. Having different records for the website and the e-mails means that you could have your site and your emails with two different companies if you would like.