Every single registered domain has at least two 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 hosting company. In this way, you've got both your site and your emails managed by the very same provider. On the lower level of the Domain Name System (DNS), nevertheless, there are a number of other records, like A and MX. The former reveals which server deals with the site for a given domain address and is always an IP address (126.96.36.199), while the latter reveals 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 Internet browser, your request is sent through the global DNS system to the provider whose NS records the domain uses and from there you could be forwarded to the servers of another service provider in case you have set an IP address of the latter as an A record for your domain. Having separate records for the site and the e-mails means that you could have your site and your e-mails with two different companies if you would like.