Dual core processor is a general term for a CPU that has two independent processors on the same unit. The advantage of this is that each processor can handle different instructions at the same time from different tasks.The biggest advantage of this comes from when a user is multitasking multiple applications at the same time, or when a specific application is programmed to take advantage of both cores unlike the pentium 4.But dual core & core2duo processors are upgraded versions of P 4.Photoshop is one such application that can use multiple cores well. Applications that aren't programmed to take advantage of multiple cores do get a slight boost in performance, but nowhere nearly as much as one that is designed for multiple core processing
Core 2 Duo is Intel's brand of a dual core processor. AMD also makes dual core processor, as do other companies. Core 2 Duo is currently considered the performance/value leader for the mainsteam dual core market.
Core Duos are also dual core processor that are the first generation of Intel's core duo design. They can process 32 bit instructions (windows XP), but not 64bit instructions. Core 2 Duo is the 2nd generation of that specific processor line, and along with many other improvements, can also handle 64 bit instructions as well (most valuable with upcoming 64 bit versions of Windows Vista). Currently, there are not that many 64 bit applications out there, so this is not as important currently, but rather more of an example of 'futureproofing'.
Now, i will tell you the main difference between the dual core & the core2duo processor. See both the processor are built on P4 platform.In dual core processor the processor is only one but while processing it acts as if it has two cores.But in core2duo there are really two cores.Now, dual core acts as having 2 cores on paper but has only one core.Means it only works as if it has two cores,but in real has only one.In core2duo it has in real two cores & it works like that.