When you add a domain as hosted in some account, you usually set a pair of Name Servers to point it to that particular company. On their end, 3 records are set up automatically the moment the domain address is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the domain address where its website is, while the other two are alphanumeric and they show the server that handles the emails for that specific domain name. The website and the e-mail hosting are typically thought to be one thing, while they're in fact two different services. Having independent records for them will permit you to have them with different providers if you would like. For example, some new service provider could have exceptional uptime for your website, but you may not want to switch your e-mails from your current host and by employing an A record to point the Internet domain to the first and MX records to have the e-mails with the second, you can get the best of both companies. These records are checked whenever you want to open a website or send an e-mail - in either case, the service 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 have set records different from their own, the right web/mail server will then be contacted and you will see the needed site or your email will be delivered.