Any time you add a domain name as hosted in some account, you typically set a pair of Name Servers to point it to that specific provider. On their end, three records are created automatically the moment the domain address is added - one A record and two MX records. The first one is a numeric address, or IP address, that “tells” the domain address where its website is, while the other two are alphanumeric and they reveal the server that manages the e-mails for that particular domain address. The website and the e-mail hosting are usually considered to be one thing, when they're in reality two different services. Having independent records for them will allow you to have them with different companies if you wish. As an illustration, some new service provider can have excellent uptime for your site, but you might not want to switch your e-mail messages from your current host and by employing an A record to point the domain to the former and MX records to have the emails with the latter, you could get the best of both providers. These records are checked when you want to open a site or send an email - either way, the company whose name servers are used for the domain name is going to 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 are going to see the needed website or your e-mail will be delivered.