When you add a domain name as hosted in some account, you typically set a pair of Name Servers to point it to that particular company. On their end, 3 records are created automatically when 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 indicate the server that manages the e-mails for that specific domain. The website and the e-mail hosting are usually perceived as one thing, while they are in reality two different services. Having separate records for them will permit you to have them with different providers if you'd like. For example, some new company may have excellent uptime for your site, but you may not want to switch your e-mails from your current host and by employing an A record to point the domain to the former and MX records to have the emails with the latter, you could get the best of both companies. These records are checked when you want to open a website or send an e-mail - either way, the provider whose name servers are used for the domain name will be contacted to retrieve the A and MX records and if you have 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 will be delivered.