When you add a domain as hosted in some account, you usually set a pair of Name Servers to direct it to that specific company. On their end, 3 records are set up automatically right after the domain address is added - one A record and two MX records. The former is a numeric address, or IP address, that “tells” the Internet domain where its website is, while the other two are alphanumeric and they show the server that manages the emails for that specific domain. The website and the email hosting are usually considered to be one thing, when they're in fact two different services. Having different records for them will enable you to have them with different providers if you want. As an illustration, some new company might have excellent uptime for your site, but you might not want to switch your emails from your current host and by using an A record to point the Internet domain to the former and MX records to have the e-mails with the second, you can get the best of both companies. These records are checked when you wish to open a site or send an email - in either case, the service 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're going to see the needed site or your e-mail is going to be delivered.