Every single 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 domain to the servers of a specific web hosting company. This way, you have got both your website and your e-mails handled by the exact same provider. On the lower level of the Domain Name System (DNS), however, there are a number of other records, like A and MX. The former reveals which server handles the website for a given domain address and is always an IP address (126.96.36.199), while the latter shows which server deals with the emails and is always an alphanumeric string (mx1.domain.com). As an example, any time 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 another provider provided you have set an IP address of the latter as an A record for your domain name. Having separate records for the website and the e-mails means you can have your website and your emails with 2 different companies if you would like.