Each 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 certain web hosting provider. This way, you have got both your website and your emails managed by the exact same service provider. On the lower level of the Domain Name System (DNS), on the other hand, there are lots of other records, for example A and MX. The former reveals which server deals with the website for a given Internet domain and is always an IP address (188.8.131.52), while the latter shows which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). For example, whenever 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 sent to the servers of a different company provided you have set an IP address of the latter as an A record for your domain. Having separate records for the website and the emails suggests that you could have your website and your emails with two different companies if you'd like.