Whenever you add a domain as hosted in some account, you normally set a pair of Name Servers to direct it to that specific company. On their end, 3 records are set up automatically as soon as the domain name is added - one A record and two MX records. The first one 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 domain name. The website and the email hosting are generally perceived as one thing, while they are in fact two different services. Having independent records for them will enable you to have them with different companies if you'd like. For instance, some new service provider may have superb uptime for your website, but you might not want to switch your e-mails from your current host and by using an A record to point the domain address to the first and MX records to have the e-mails with the latter, you can 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 Internet domain will 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 site or your e-mail will be delivered.