When you add a domain name as hosted in some account, you usually set a pair of Name Servers to point it to that particular service provider. On their end, three records are set up automatically when the Internet domain is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the domain name where its site is, while the other two are alphanumeric and they indicate the server that manages the e-mails for that particular domain. The website and the e-mail hosting are typically regarded as one thing, when they're in reality two different services. Having independent records for them will permit you to have them with different providers if you wish. As an example, some new company could have superb uptime for your website, 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 name to the first and MX records to have the e-mails with the second, you will get the best of both providers. These records are checked when you want to open a site or send an e-mail - in either case, the service provider whose name servers are used for the domain address 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 are going to see the needed website or your e-mail is going to be delivered.