Any time you add a domain name as hosted in some account, you normally set a pair of Name Servers to point it to that particular service provider. On their end, 3 records are created automatically when 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 where its website is, while the other two are alphanumeric and they indicate the server that deals with the emails for that particular domain. The site and the email hosting are often perceived as one thing, while they are actually two different services. Having independent records for them will enable you to have them with different providers if you'd like. As an illustration, some new provider might have excellent uptime for your website, but you might not want to switch your emails from your current host and by employing an A record to point the domain address to the former and MX records to have the emails with the latter, you will get the best of both providers. These records are checked when you want to open a site or send an email - in either 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 right web/mail server will then be contacted and you will see the needed site or your e-mail is going to be delivered.