Whenever you add a domain as hosted in some account, you typically set a pair of Name Servers to point it to that particular service provider. On their end, three records are set up automatically the moment the domain 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 particular Internet domain. The site and the email hosting are typically regarded as one thing, when they're in reality two different services. Having independent records for them will permit you to have them with different providers if you would like. As an illustration, some new provider could have outstanding uptime for your site, but you might 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 emails with the latter, you could get the best of both companies. These records are checked whenever you want to open a site or send an e-mail - either way, the service provider whose name servers are used for the domain address 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're going to see the needed site or your email is going to be delivered.
