DNS can be considered something similar to a phone book. When you move from one location to another, your name stays the same, but your phone number may change.
In order to point your name to the new phone number, you must contact the telephone service provider so they assign you the new phone number and update all directory information to reflect you as pointing to this new phone number.

In this way, the IP number can be compared to a phone number: When someone calls http://www.example.com/, your ISP looks at the DNS server, and asks "how do I contact example.com?" The DNS server responds: "It can be found at 198.105.232.4".
As the Internet understands it, this can be considered the phone number for the server, which houses the http://www.example.com web site.

The DNS records for your domain are kept on your hosting server in the place called DNS zone. When you register a domain by means of the control panel, all DNS records are automatically created for you, but in some rare cases you may need to add custom records to your DNS zone.
An example would be when you want all email to be processed by an external mail server rather than by the built-in mail system. However, such user intervention requires knowledge of DNS configuration and clear understanding of what is to be done.

To create a custom record to your DNS zone, do the following:

• Click Domains in your control panel home page.
  
• Select the domain if you have more than one.
  
• On the page that appears, click the Edit icon in the DNS Configuration field:
  

This link will take you to the DNS Configuration page:

On this page you can see several blocks of DNS records. Some are built-in and non-removable; others are user-defined and can be deleted. Built-in MX records require special consideration: they can be removed by disabling mailservices for this domain., but all e-mail resources, including mailboxes, forwarders, and autoresponders will also be deleted. You can add any type of DNS records by clicking an appropriate link. You will be asked to enter corresponding DNS data.

Adding Custom A Records

Normally, A records are used to map domain names and web server IP's.
If you have selected A record, the following page appears:

Name: enter the string to map to the web server.
TTL: set how many seconds will elapse before the record is refreshed in the DNS cache.
Data: enter the IP of the web server.
WARNING: Please pay attention to $ORIGIN when you add an A record.

Adding Custom MX Records

Custom MX records should be added when you want to use your external mail servers to process your e-mail. To use your external servers instead of those you get by default, you need to disable mail service on the Domain Settings page of your control panel. To use the default mail servers in addition to those you get by default, you need to keep mail service enabled in the control panel.

The priority of the custom MX record will define whether your external servers will act as secondary or primary. For instance, if you set the priority of the custom MX record higher than 10 (e.g. 11), your external mail server will be used as secondary.
If you set the priority of the custom MX record lower than 10 (e.g. 9), your external mail server will be used as primary. In the latter case, your mail will be sent to your external mail server until it goes down or becomes otherwise inaccessible. Then the default mail server will take over.

When you enable mail service in the control panel, an MX record is created automatically in the DNS zone. If mail service is disabled, this built-in MX record remains in the DNS zone, and you can remove it manually using the control panel interface.

If you have selected MX record, the following page appears:

Name: your local domain name. If you leave the Name field blank, all mail will be redirected for the base zone.

Data: the priority of the record and mail domain name (not the IP) mail will be forwarded to.

IMPORTANT: To add an MX record for the base domain, leave the Name field empty.

Adding Custom CNAME Records

Finally, CNAME records are used to map aliases with domain names.
If you have selected CNAME record, the following page appears:

Name: The alias you give to the real host name.

TTL: set how many seconds will elapse before the record is refreshed in the DNS cache.

Data: The real name of the host you create an alias to. This must be an official host name. It cannot be an alias. A CNAME-record should always point to an A-record to avoid circular references.

WARNING: Please pay attention to $ORIGIN when you add a CNAME record.