Each 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 address to the servers of a particular website hosting company. In this way, you have got both your site and your e-mails managed by the same provider. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, for instance A and MX. The first one shows which server handles the website for a given Internet domain and is always an IP address (18.104.22.168), while the second one shows which server handles the e-mails and is always an alphanumeric string (mx1.domain.com). For example, any time you type a domain name in your 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 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 address. Having independent records for the website and the emails suggests that you can have your site and your emails with two different companies if you'd like.