Well, in a crowd of different processors available today and many new ones coming out eventually, I have seen many people being confused in choosing processor while buying a computer. Some dont even dare to care about the specs of processor (only clock speed and cache memory is noticed)(I intensionally did not mention laptop in here, cause in Nepal we hardly get to make a laptop of our own configuration). I am as well one of us who is confused in this case. So thought to present a rough idea on different processors - This writing is only a basic idea but works for Nepali market pretty well.
And ya this idea is for only Intel Processors. I think AMD processors are not common than Intel(in Nepal). will include about AMD processors as well in next writing.
I shall start with Dual Core Processors because processors older than that are almost out of run at the moment. (at least for us involved in IT study)

# DualCore and Core2Duo Processors are almost same thing. DualCores are low configuration and low cost version of Core2Duo processors. Both DualCore and Core2Duo have 2 cores embedded in a single chip and number of threads is also 2. This means single logical core per physical core. Both the processors are dual-core series but the one named as DualCore shares cache with the two cores whereas in Core2Duo, independent cores have independent cores

# Core2Quad Processors are multi chip modules consisting of two chips as those used in Core2Duo forming a quad-core processor (meaning these processors will provide double the performance than dual-core processors). They have 4 cores and 4 threads. (May be these processors can be understood as dual-core Core2Duo processors :))

#Core2Extreme Processors are more advanced version of Core2Duo and Core2Quad Processors, with a higher clock frequency. And they are specially capable of high overclocking.

#2010 Intel core Processors (as told by Intel)
Core-i3, Core-i5 and Core-i7 processors fall in this category.

These Processors are Nehalem microarchitecture based processors. They can be considered from low end processor (i3) to high end (i7) from Intel. These processors have integrated GPU (Graphics Processing Unit) and almost same architecture These processors have 256KB L2 cache per core available as per the processor and upto 12 MB shared L3 cache. These Processors contain L3 cache.
*Core-i3 processors are dual-core processors i.e contain two physical processors and contain Intel Hyper Threading Technology which increases the thread number to 4. core-i3 processors does not support Intel Turbo Boost Technology, meaning - turbo over clocking is not available in i3 processors.

*Core-i5 Processors are as well dual-core processors, but with higher configuration than core i3 processors. These processors also support Intel Turbo Boost Technology so that if any application runs out of processor timing or working, the system auto overclocks to a factory allowed higher clock rakge. They contain 2 physical cores and 4 threads as well. i5-750, i5-760,i5-75S are exception i5 processors that contains 4 cores and 8Mb cache(these three model contain intel turbo boost technology but does not contain intel hyper threading technology)

*Core-i7 Processors are enhanced version of Intel Quad-Core Processors. They support Hyper threading technology hence have 8 threads in 4 physical cores. (Except for i7-970 which is based on 32nm technology and contains 6 physical cores and 12 threads). These Processors support Intel Turbo Boost feature as well as Intel Hyper Threading Technology)
In comparision to the old generation processors, these processors have more potential.
I think this helps to some extend on buying a good processor. This writing is based on my research. Please fell free to correct the errors :). I will write about AMD processors in next writing.