Whenever you add a domain as hosted in some account, you usually set a pair of Name Servers to point it to that specific provider. On their end, three records are set up automatically right after the domain address is added - one A record and two MX records. The former is a numeric address, or IP address, that “tells” the domain where its site is, while the other two are alphanumeric and they show the server that deals with the emails for that particular Internet domain. The site and the email hosting are typically considered to be one thing, when they are actually two different services. Having separate records for them will enable you to have them with different companies if you'd like. As an example, some new service provider might have superb uptime for your website, but you might not want to switch your emails 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 whenever you want to open a website or send an email - in either case, the company whose name servers are used for the Internet domain 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 email is going to be delivered.