When you add a domain as hosted in some account, you usually set a pair of Name Servers to direct it to that specific provider. On their end, 3 records are created automatically as soon as the Internet domain is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the domain name where its site is, while the other two are alphanumeric and they reveal the server that handles the e-mails for that particular domain. The website and the e-mail hosting are typically perceived as one thing, while they are in fact two different services. Having separate records for them will permit you to have them with different providers if you wish. As an example, some new service provider could have superb 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 emails with the latter, you will get the best of both companies. These records are checked when you wish to open a website or send an e-mail - in any case, the company whose name servers are used for the Internet domain 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're going to see the needed website or your email is going to be delivered.