Any time you add a domain as hosted in some account, you normally set a pair of Name Servers to point it to that particular provider. On their end, 3 records are set up 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, which “tells” the Internet domain where its website is, while the other two are alphanumeric and they show the server that handles the emails for that particular domain address. The website and the e-mail hosting are typically perceived as one thing, while they're actually two different services. Having separate records for them will allow you to have them with different providers if you wish. For instance, some new company can have excellent uptime for your site, but you may not want to switch your e-mail messages from your current host and by using an A record to point the domain to the former and MX records to have the e-mails with the latter, you could get the best of both providers. These records are checked when you wish to open a website or send an email - in either case, 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've set records different from their own, the right web/mail server will then be contacted and you are going to see the needed site or your email will be delivered.