When you add a domain name as hosted in some account, you normally set a pair of Name Servers to point it to that specific service provider. On their end, 3 records are created automatically the moment the Internet domain is added - one A record and two MX records. The first one is a numeric address, or IP address, which “tells” the domain address where its site is, while the other two are alphanumeric and they reveal the server that handles the emails for that specific Internet domain. The website and the email hosting are generally considered to be one thing, when they're in fact two different services. Having separate records for them will enable you to have them with different companies if you'd like. For instance, some new service provider can have excellent uptime for your website, but you might not want to switch your emails from your current host and by employing an A record to point the Internet domain to the former and MX records to have the emails with the second, you can get the best of both providers. These records are checked whenever you want to open a site or send an e-mail - in either case, the provider whose name servers are used for the domain address will be contacted to retrieve the A and MX records and if you've set records different from their own, the correct web/mail server will then be contacted and you will see the needed site or your e-mail will be delivered.