Adding to Pilgrim's description:
If you want a Domain to point to another one "within the same main account" then use Parked, not Add-on. A Parked domain automatically re-directs to the main account, but allows the use of another URL to point to it. So
http://parkeddomain.com/ will point to
http://mainaccount.com/ but use it's own URL. This means, no matter which URL is used, the same pages will be shown.
No directories are created for Parked domains, only an additional code added to the httpd.conf file. All Stats for Parked domains are included within the main account Stats. They are not shown seperately as they are for Sub-domains / Add-on domains, which is something to remember. eMail is also sent to the main account address (using the URL of the Parked domain) although, replies can use the Parked Domain name -- which one would setup in their eMail program.
Experience is the best teacher so a few registered Domain names, used for your purposes in figuring out WHM/Cpanel, is always handy.
