Whenever you add a domain name as hosted in some account, you typically set a pair of Name Servers to direct it to that particular provider. On their end, 3 records are set up automatically the moment the domain address is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the domain address where its website is, while the other two are alphanumeric and they reveal the server that manages the emails for that particular domain. The site and the email hosting are generally perceived as one thing, while they're in reality two different services. Having separate records for them will permit you to have them with different companies if you would like. As an illustration, some new provider may have exceptional 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 domain to the first and MX records to have the emails with the latter, you will get the best of both providers. These records are checked when you wish to open a site or send an e-mail - in any case, the provider whose name servers are used for the domain name will 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 e-mail is going to be delivered.