Whenever you add a domain as hosted in some account, you usually set a pair of Name Servers to direct it to that particular provider. On their end, three records are set up automatically right after the domain is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the domain name where its site is, while the other two are alphanumeric and they show the server that manages the emails for that specific Internet domain. The website and the e-mail hosting are often considered to be one thing, while they're in fact two different services. Having different records for them will permit you to have them with different companies if you would like. For example, some new service provider could 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 domain name to the first and MX records to have the e-mails with the latter, you will get the best of both providers. These records are checked when you wish to open a website or send an e-mail - in any case, the provider 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 correct web/mail server will then be contacted and you are going to see the needed website or your e-mail will be delivered.