Any time you add a domain as hosted in some account, you normally set a pair of Name Servers to direct it to that particular company. On their end, 3 records are created automatically the moment 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 domain name where its website is, while the other two are alphanumeric and they reveal the server that deals with the e-mails for that specific domain name. The site and the e-mail hosting are generally perceived as one thing, when they are in fact 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 might have exceptional uptime for your site, but you might not want to switch your e-mails from your current host and by using an A record to point the domain to the first and MX records to have the e-mails with the second, you could get the best of both companies. These records are checked whenever you want to open a website or send an email - either way, the service provider whose name servers are used for the Internet domain 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.