Advantages
Dual-core processors are a fairly new innovation built by both
major processor manufacturers (Intel Core Duo / Core 2 Duo and AMD Athlon
64 X2).
• Multitasking: Each processor has two processing centres (cores) for a theoretical
maximum of twice the operating power and for better multitasking.
Major advantages of dual core processors are evident when doing heavy
multitasking, such as encoding video and playing video games at the same
time.
• Application Support: Newer applications are being written to take advantage
of this technology by using a technique known as Multithreading.
• Power Saving: Dual core processors (especially Intel Core Duo) have the
ability to turn off one of their cores when application demand is low to
save power.
Disadvantages
• Support: Older programs (with certain notable exceptions) do not support
multithreading and may run very slightly slower on dual core CPUs.
Multi-core Future? Quad core technology is finally here, and more and more
programs are being built to take advantage of multiple cores. The large chip
makers are discussing CPU’s with eight, sixteen, even thirty two cores in the
coming years. Only time and experience will tell how the advantages we are
seeing with duo and quad core configurations will scale.
Descriptions
Often in advertisements (especially for prebuilt systems) a processor will be
described briefly, like this:

Pentium 4 at 3.2 GHz
But theres more to it than that, a more detailed specification would read as
follows:
Intel Pentium 4 3.2GHz LGA775 FSB800 HT L2-2MB
Which parses out to:
Model: Intel Pentium 4
Clock Speed: 3.2GHz (=3200MHz)
Interface: Land Grid Array 775
Frontside Bus: 800 Mhz
Other Spec: HyperThreading technology
L2-Cache: 2MB (=2048 kB)
So we can see that while 3.2 GHz is a screaming fast clock speed, this
processor might not be as fast as, say, a processor with a 4 megabyte L2 cache,
a 1066 Mhz front side bus and two cores, even if that processor runs at a slower
clock speed.