Every registered domain name has a minimum of two Name Server records that show where it's hosted i.e. by using these records you direct your Internet domain to the servers of a particular hosting company. This way, you have got both your website and your e-mails managed by the same 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 shows which server deals with the website for a given domain and is always an IP address (123.123.123.123), while the latter reveals which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). For example, whenever you enter a domain in your browser, your request is directed through the global DNS system to the provider whose NS records the domain address uses and from there you will 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 different records for the website and the e-mails suggests that you can have your website and your emails with two different providers if you wish.