When you add a domain name as hosted in some account, you normally set a pair of Name Servers to point it to that specific company. On their end, three records are created automatically right after the domain address 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 indicate the server that handles the emails for that particular domain. The website and the email hosting are usually thought to be one thing, when they're actually two different services. Having independent records for them will allow you to have them with different providers if you wish. For example, some new service provider may have excellent 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 address to the first and MX records to have the e-mails with the second, you could get the best of both providers. These records are checked when you want to open a website or send an email - either way, 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 right web/mail server will then be contacted and you are going to see the needed website or your email is going to be delivered.