Whenever you add a domain as hosted in some account, you typically set a pair of Name Servers to direct it to that specific provider. On their end, 3 records are set up automatically right after the domain is added - one A record and two MX records. The first one is a numeric address, or IP address, which “tells” the domain where its site is, while the other two are alphanumeric and they indicate the server that deals with the e-mails for that specific domain name. The website and the email hosting are generally considered to be one thing, when they are in fact two different services. Having different records for them will permit you to have them with different companies if you'd like. For example, some new company might have exceptional uptime for your website, but you might not want to switch your e-mail messages from your current host and by using an A record to point the domain name to the first and MX records to have the e-mails with the second, you can get the best of both providers. These records are checked when you wish to open a website or send an email - in either case, the company whose name servers are used for the Internet domain is going to be contacted to retrieve the A and MX records and if you have 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 email will be delivered.