When you add a domain name as hosted in some account, you typically set a pair of Name Servers to direct it to that specific service provider. On their end, 3 records are set up automatically as soon as the Internet domain 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 site is, while the other two are alphanumeric and they show the server that manages the e-mails for that particular domain name. The website and the e-mail hosting are usually perceived as one thing, while they are actually two different services. Having separate records for them will allow you to have them with different companies if you wish. For instance, some new company could have fantastic uptime for your site, but you may 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 emails 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 - either way, the provider whose name servers are used for the domain address is going to be contacted to retrieve the A and MX records and if you've set records different from their own, the correct web/mail server will then be contacted and you are going to see the needed site or your e-mail is going to be delivered.