When you add a domain name as hosted in some account, you typically set a pair of Name Servers to direct it to that particular company. On their end, three 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 where its site is, while the other two are alphanumeric and they indicate the server that deals with the e-mails for that specific domain. The website and the email hosting are typically thought to be one thing, while they are in reality two different services. Having separate records for them will enable you to have them with different providers if you wish. For instance, some new service provider can have exceptional uptime for your website, but you may not want to switch your e-mails 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 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 provider whose name servers are used for the domain will be contacted to retrieve the A and MX records and if you've set records different from their own, the correct web/mail server will then be contacted and you'll see the needed website or your e-mail is going to be delivered.