Every registered domain has no less than 2 Name Server records which show where it's hosted i.e. by using these records you direct your Internet domain to the servers of a specific website hosting company. This way, you have got both your site and your emails handled by the very same company. On the lower level of the Domain Name System (DNS), however, there are a number of other records, for instance A and MX. The former shows which server manages the site for a given domain address and is always an IP address (18.104.22.168), while the latter shows which server manages the emails and is always an alphanumeric string (mx1.domain.com). For instance, whenever you type a domain in your Internet browser, your request is directed 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 company if you have set an IP address of the latter as an A record for your domain. Having independent records for the website and the e-mails means that you could have your site and your emails with 2 different companies if you'd like.