Every single registered domain has no less than two Name Server records which show where it is hosted i.e. by using these records you point your domain address to the servers of a specific website hosting company. That way, you've got both your website and your e-mails managed by the very same company. On the lower level of the Domain Name System (DNS), nevertheless, there are a number of other records, such as A and MX. The former reveals which server handles the site for a given domain name and is always an IP address (18.104.22.168), while the latter indicates which server handles the e-mails and is always an alphanumeric string (mx1.domain.com). For instance, any time you enter a domain address in your browser, your request is forwarded through the global DNS system to the provider whose NS records the domain address uses and from there you may be forwarded to the servers of another provider in case you have set an IP address of the latter as an A record for your domain name. Having different records for the website and the emails suggests that you can have your site and your emails with two different companies if you wish.