Whenever you add a domain as hosted in some account, you usually set a pair of Name Servers to direct it to that specific provider. On their end, three records are created automatically right after the domain is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the Internet domain where its website is, while the other two are alphanumeric and they indicate the server that manages the emails for that specific domain name. The website and the email hosting are generally regarded as one thing, when they are in fact two different services. Having independent records for them will enable you to have them with different providers if you wish. For instance, some new service provider might have exceptional uptime for your website, 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 former 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 want to open a site or send an email - either way, 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'll see the needed site or your e-mail is going to be delivered.