Whenever you add a domain name as hosted in some account, you typically set a pair of Name Servers to point it to that specific service provider. On their end, three records are set up automatically when 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 address where its website is, while the other two are alphanumeric and they reveal the server that manages the emails for that specific domain address. The website and the e-mail hosting are generally considered to be one thing, when they're actually two different services. Having separate records for them will permit you to have them with different companies if you want. As an illustration, some new company could have outstanding uptime for your site, but you might not want to switch your e-mails from your current host and by employing an A record to point the Internet domain to the first and MX records to have the emails with the latter, you could get the best of both providers. These records are checked when you wish to open a website or send an email - in any case, 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're going to see the needed site or your e-mail will be delivered.