When you add a domain name as hosted in some account, you normally set a pair of Name Servers to direct it to that particular provider. On their end, 3 records are created automatically as soon as the domain name 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 site is, while the other two are alphanumeric and they show the server that handles the e-mails for that particular domain. The site and the email hosting are often considered to be one thing, when they are in reality two different services. Having separate records for them will allow you to have them with different providers if you wish. For example, some new service provider can have superb 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 name to the first and MX records to have the e-mails with the second, you could get the best of both companies. These records are checked when you want to open a website or send an e-mail - in either case, the company whose name servers are used for the domain address 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'll see the needed site or your email will be delivered.