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 particular service provider. On their end, 3 records are set up automatically as soon as the Internet domain is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the domain where its website is, while the other two are alphanumeric and they show the server that deals with the emails for that particular domain name. The site and the e-mail hosting are typically regarded as one thing, when they're in fact two different services. Having separate records for them will allow you to have them with different companies if you want. As an illustration, some new service provider may have exceptional uptime for your website, but you might not want to switch your emails from your current host and by employing an A record to point the Internet domain to the first and MX records to have the e-mails with the latter, you could get the best of both companies. These records are checked whenever you want to open a site or send an email - in any case, the service provider whose name servers are used for the domain 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'll see the needed site or your email will be delivered.