Duo processor Technology? There seems to be a lot of confusion and fudging between these 2 terms used by PC/Laptop makers.

What exactly is the difference between these two. from what I read I understand that core 2 duo is a intel chip like Pentium and both use the dual core technology ie have two cores on the same chip.

Also it appears that for this dual core technology to work optimally we need a o/s which can handle multithreading. Also the applications have to be tuned to use this technology.

Given these how beneficial is it to end users. Specifically why should one go for core 2 duo instead of a normal intel Pentium dual core machine.