Back in the day buying a processor was as simple as looking at the megahertz or gigahertz and purchasing based on the bigger number. I know there's more to it than that like onboard cache and what-not, but in comparison to what we've got to work with today, life seemed simpler back then.
So, for example, what's the difference between Core 2 and Core 2 Duo?
Let's explore!
Core 2 is the successor to Intel's Pentium D line of processors, which was basically two Pentium 4 “Prescott” processors duct-taped together and called Dual Core. Core 2 is this, only with a more refined construction, making it more efficient in terms of both power and consumption of power. This design is perfect for laptops.
Core 2 Duo, on the same hand, is the successor to the Core 2 architecture, but is designed for desktops and laptops. Once again, more powerful and more energy efficient than previous models.
It's just a matter of variants at this point, with the familiar “gigahertz” numbers buried deep within the processor's specifications sheet. You'll see something like Core i7 950, which just so happens to have multiple processors running at 3.06ghz.
The next model up, the 965 Extreme, clock in at 3.20ghz per processor. Remember to search the manufacturer's website for more info, and if you're still confused, Wikipedia has some decent information on all of the current processors on the market.