Its called masked forwarding, All that you need is a parked domain (No need for Hosting) then you can set this up easily in the settings of the domain name. You can set up a standard redirection or Mask the redirection.....

If you mask the redirection the following will occur..

www.xyz.com -> when redirected to hxxp://xxxxxxx.fuelwater1.hop.clickbank.net/ will still only apear as www.xyz.com in the browser window.

I hope that makes sense..... If you are talking about hiding your affiliate links on a review site you need to look up link "cloaking", Id go into further detail but im in a rush.... just search for this on BHW there is heaps of good threads..