if buyng new, these are old cpu's. "core 2" is the model of processor(old model) "duo" means it has 2 cpu cores (dual core.). Having said that a core 2 duo is fine for online web browsing.
A C2D is can also handle recording streaming video (Netflix etc), playing Bluray and HD videos, running a VM,
video editing with Sony Vegas and Power Director, playing Crysis Warhead at 1920x1080 on gamer settings
and much more
A pentium 4 or amd athlon single core are online browser computers LOL