Every registered domain has a minimum of 2 Name Server records that show where it's hosted i.e. by using these records you point your domain address to the servers of a particular website hosting company. In this way, you have got both your website and your e-mails managed by the exact same company. On the lower level of the Domain Name System (DNS), nevertheless, there is a variety of other records, for example A and MX. The first one reveals which server handles the website for a given domain and is always an IP address (123.123.123.123), while the latter shows which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). As an illustration, whenever you enter a domain in your browser, your request is sent through the global DNS system to the provider whose NS records the domain uses and from there you may be forwarded to the servers of another provider provided you have set an IP address of the latter as an A record for your domain address. Having different records for the website and the e-mails means that you could have your website and your emails with two different companies if you wish.