When you add a domain name as hosted in some account, you normally set a pair of Name Servers to point it to that particular service provider. On their end, 3 records are created automatically as soon as the domain is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the domain where its website is, while the other two are alphanumeric and they indicate the server that deals with the emails for that specific Internet domain. The site and the e-mail hosting are typically considered to be one thing, while they are actually two different services. Having separate records for them will permit you to have them with different companies if you wish. As an illustration, some new company could have superb uptime for your website, but you might not want to switch your e-mail messages from your current host and by employing an A record to point the Internet domain to the former and MX records to have the e-mails with the latter, you can get the best of both companies. These records are checked when you want to open a site or send an e-mail - in any 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've set records different from their own, the right web/mail server will then be contacted and you will see the needed website or your email is going to be delivered.