Whenever you add a domain 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 created automatically as soon as the domain is added - one A record and two MX records. The first one is a numeric address, or IP address, which “tells” the Internet domain where its site is, while the other two are alphanumeric and they indicate the server that deals with the emails for that particular domain name. The website and the e-mail hosting are typically regarded as one thing, while they are actually two different services. Having separate records for them will allow you to have them with different providers if you would like. As an illustration, some new company can have superb uptime for your website, 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 former and MX records to have the emails with the latter, you will get the best of both providers. These records are checked when you wish to open a website or send an email - either way, the service provider whose name servers are used for the domain address 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 will see the needed site or your email will be delivered.