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 provider. On their end, three records are created automatically right after the domain address 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 site 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 e-mail hosting are typically thought to be one thing, when they are in reality two different services. Having separate records for them will enable you to have them with different companies if you'd like. For instance, some new company can have excellent uptime for your site, but you may not want to switch your e-mails from your current host and by employing an A record to point the domain address to the former and MX records to have the emails with the latter, you could get the best of both providers. These records are checked whenever you want to open a site or send an email - in either case, the company whose name servers are used for the domain name 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 are going to see the needed site or your e-mail will be delivered.