Whenever you add a domain name as hosted in some account, you normally set a pair of Name Servers to point it to that specific company. On their end, 3 records are created automatically right after the domain name is added - one A record and two MX records. The former is a numeric address, or IP address, that “tells” the domain name where its website is, while the other two are alphanumeric and they reveal the server that deals with the emails for that specific domain address. The website and the e-mail hosting are usually thought to be one thing, while they are in reality two different services. Having different records for them will allow you to have them with different providers if you would like. As an example, some new service provider may have superb 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 domain to the first and MX records to have the emails with the second, you could get the best of both providers. These records are checked whenever you want to open a website or send an e-mail - either way, the service provider whose name servers are used for the domain name will 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'll see the needed website or your e-mail will be delivered.