Any time 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 set up automatically when 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 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 generally regarded as one thing, when they are in fact two different services. Having separate records for them will permit you to have them with different companies if you'd like. For example, some new provider may have outstanding uptime for your website, but you may not want to switch your emails from your current host and by employing an A record to point the domain to the former 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 want to open a site 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 will see the needed site or your email is going to be delivered.