Whenever you add a domain name as hosted in some account, you normally set a pair of Name Servers to direct it to that specific service provider. On their end, three records are created automatically when the Internet domain is added - one A record and two MX records. The first one is a numeric address, or IP address, which “tells” the domain where its website is, while the other two are alphanumeric and they reveal the server that handles the e-mails for that specific Internet domain. The site and the email hosting are generally thought to be one thing, when they're actually two different services. Having independent records for them will permit you to have them with different companies if you want. For example, some new provider could have outstanding uptime for your site, but you may 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 emails with the latter, you can get the best of both providers. These records are checked when you want to open a website or send an email - in any case, the provider whose name servers are used for the 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 e-mail is going to be delivered.