Whenever you add a domain name as hosted in some account, you normally set a pair of Name Servers to point it to that specific service provider. On their end, three records are created automatically as soon as 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 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 e-mail hosting are usually considered to be one thing, while they are in reality two different services. Having independent records for them will allow you to have them with different providers if you wish. As an illustration, some new service provider might have outstanding uptime for your site, but you might not want to switch your e-mails from your current host and by employing an A record to point the domain name to the former and MX records to have the e-mails with the latter, you could get the best of both providers. These records are checked when you wish to open a site or send an e-mail - in either case, the company 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 are going to see the needed website or your email will be delivered.