What are cores in a video card

[ralphf926]

I want to replace my video card and I'm looking at 2 MSI cards: GeForce GTX 560(Fermi) and GTX 560-TI(Fermi). I was all set to buy the GTX 560 when I read a comment that it is worth the extra money to buy the GTX 560-Ti because it has 48 more cores, 384 vs 336. What are cores and in my case are they worth the extra $28 for the GTX 560-TI. As far as I can determine the rest of the specs are the same. Thanks for any input.

 

[Mousemonkey]

The cores are what give the card its power and the more the better, the GTX560 non Ti is also little more than an OC'd GTX460.