You can setup two or more domain names pointing to a same set of web pages (i.e. www.domainA.com/index.htm and www.domainB.com/index.htm both pointing to the same index.htm), this is done by "parking" domain www.domainA.com onto domain www.domainB.com.
Another Example: Your have two business domain name www.mygoodbusiness.co.nz and www.myinnovation.co.nz. You have hired a web designer to build a beautiful website for one of your domain www.mygood business.co.nz, but you have run out of budget to pay for a second website for your other domain www.myinnovation.co.nz at the moment, and you need to use the email accounts on this domain www.myinovations.co.nz and you don't want people to see a bunch of ads shown by your domain registrar when your potential clients enter www.myinovations.co.nz in their browser. What should you do ? setup www.myinnovations.co.nz as parked domain ! By parking www.myinnovation.co.nz on top of www.mygoodbusiness.co.nz, all URLs requests for www.myinnovation.co.nz will automatically go to www.mygoodbusiness.co.nz, this way your potential clients can still get contact info on the web page of www.mygoodbusiness.co.nz to reach you.
To park a domain name:
Click Parked Domains button in your domain hosting account control panel.
Enter the new domain name that you wish to park on the master domain name of this hosting account New Domain Name field.
Click Add button and the parking is done.
NOTE: Please ensure the nameserver record for the new domain is changed and resolved to this server before attempt to setup parked domain, otherwise server will reject the parking request