When you add a domain as hosted in some account, you normally set a pair of Name Servers to point it to that specific company. On their end, 3 records are set up automatically as soon as the domain is added - one A record and two MX records. The first one is a numeric address, or IP address, which “tells” the domain address where its website is, while the other two are alphanumeric and they indicate the server that deals with the emails for that particular Internet domain. The website and the e-mail hosting are typically considered to be one thing, when they are in reality two different services. Having different records for them will enable you to have them with different companies if you wish. For example, some new company can have excellent uptime for your site, but you might 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 second, you could get the best of both companies. These records are checked whenever you want to open a website or send an email - in any case, the service provider whose name servers are used for the domain is going to be contacted to retrieve the A and MX records and if you have set records different from their own, the correct web/mail server will then be contacted and you will see the needed website or your e-mail will be delivered.