When you add a domain name as hosted in some account, you usually set a pair of Name Servers to point it to that particular company. On their end, 3 records are set up automatically the moment the domain address is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the Internet domain where its website is, while the other two are alphanumeric and they show the server that manages the emails for that specific domain. The website and the e-mail hosting are usually perceived as one thing, while they're in reality two different services. Having different records for them will allow you to have them with different providers if you would like. As an illustration, some new company might have outstanding uptime for your website, but you may not want to switch your e-mails from your current host and by using an A record to point the domain to the first and MX records to have the emails with the second, you can get the best of both providers. These records are checked when you want to open a website or send an email - in either case, the service provider whose name servers are used for the Internet 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 will see the needed website or your email will be delivered.