Any time you add a domain name as hosted in some account, you usually set a pair of Name Servers to direct it to that specific company. On their end, three records are set up automatically when the domain name is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the Internet domain where its website is, while the other two are alphanumeric and they reveal the server that manages the e-mails for that specific domain. The site and the email hosting are often thought to be one thing, while they are in fact two different services. Having separate records for them will allow you to have them with different companies if you would like. As an example, some new company can have exceptional uptime for your site, but you may not want to switch your e-mails from your current host and by using an A record to point the domain address to the first and MX records to have the e-mails with the second, you will get the best of both companies. These records are checked when you wish to open a site or send an e-mail - in either case, the service provider whose name servers are used for the domain will be contacted to retrieve the A and MX records and if you have set records different from their own, the correct web/mail server will then be contacted and you're going to see the needed site or your email is going to be delivered.