I've seen in the apple store site the different iMac's and the most expensive one has a quad-core processor. What does that mean? What's a quad-core processor?

a quad core cpu has 4 c processing core in one chip. think of it as 4 lanes of traffic vs 1 or2 lanes of traffic. which is faster?

A quad-core processor is a processor that can handle up to 4 times the amount a normal processor can. For example, Let's say that a single- core processor can handle 2.5 g Hz of data. Well, the quad- core processor can handle 4 times that amount of data (that is if one core of the four cores can handle that much). Most likely the cores of that processor can. A single core of a processor can handle up to 3 g Hz before it cross threads... I don't want to get into more detail...

I hope this helps. :)

Quad core is the proccesor unit, so it will run the computer more smooth and faster. The more cores the better. The higher GHz the better.

Quad-core processors are essentially four processors. This is good for gaming as it can handle more calculation per second than a dual core or single core.

Quad cores are more power full than Dual and Single cores.
Quad = 4
Dual = 2
Celron = 1

You get more power from a quad core because it has 4 cores.

a qual core is like four processors in one, witch will allow you to prefer multi tasking without problems and slowing down your computer .

It has 4 processing cores. It's basically like 4 processors in one.

It makes your computer run really fast. I just got one.