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 provider. On their end, 3 records are created automatically right after the domain address is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the domain where its site is, while the other two are alphanumeric and they reveal the server that manages the e-mails for that particular domain address. The site and the email hosting are usually regarded as one thing, while they are in reality two different services. Having separate records for them will allow you to have them with different companies if you would like. As an illustration, some new service provider can 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 Internet domain to the former and MX records to have the emails with the latter, you can get the best of both providers. These records are checked whenever you want to open a website or send an e-mail - in any case, the company 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're going to see the needed website or your e-mail will be delivered.