Any time you add a domain as hosted in some account, you usually set a pair of Name Servers to direct it to that particular service provider. On their end, three records are created automatically right after the domain name is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the Internet domain where its site is, while the other two are alphanumeric and they indicate the server that manages the e-mails for that particular domain address. The website and the email hosting are usually thought to be one thing, while they're actually two different services. Having separate records for them will permit you to have them with different companies if you want. As an example, some new provider may have fantastic 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 domain name to the former and MX records to have the e-mails with the second, you can get the best of both companies. These records are checked when you want to open a website or send an e-mail - in either case, the provider whose name servers are used for the domain name is going to be contacted to retrieve the A and MX records and if you've set records different from their own, the right web/mail server will then be contacted and you will see the needed site or your e-mail is going to be delivered.