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 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, that “tells” the domain where its website is, while the other two are alphanumeric and they indicate the server that deals with the e-mails for that particular domain. The website and the email hosting are generally considered to be one thing, while they are in fact two different services. Having independent records for them will permit you to have them with different companies if you want. As an example, some new company may have exceptional uptime for your site, but you may not want to switch your e-mail messages from your current host and by employing an A record to point the domain to the first and MX records to have the emails with the latter, you will get the best of both providers. These records are checked when you want to open a website or send an e-mail - 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 is going to be delivered.