I know duo means it has 2 cores. I also know that the LGA 775 is the type of socket it plugs into, and 65W is the power it uses. what is the 3.0 Ghz? is that the speed that it processes info? is it 3.0 Ghz per core equaling 6.0 Ghz? what is the 8400? Do i really need to know other than the bigger the number the better? Also whats the difference between wolfdale, yorkfield, kentsfield, etc. Whats the manufacturing tech, 45nm, 65 nm?
65W is technically not hw much power it uses, it is what Intel determines the cooling system for the CPU must be able to dissipate at a minimum. It would be a pain for Intel to have this value different for every single processor model, so that is why an entire line of CPUs will typically have the same Thermal Design Power, even though they have slightly different power consumptions due to different clock speeds. System builders like Dell must conform to these specifications because if they don't and something goes wrong, it's not Intel's fault.
The speed of the CPU is how many clock cycles occur per second (measured in Hertz). Rather than explaining a clock cycle, just know that a higher clock speed means a faster processor only when comparing a CPU of the same family. For example, you can not say that a 3GHz Pentium 4 is faster than a 2.4GHz Core 2 Duo, because that couldn't be further from the truth. However, a 3GHz Core 2 Duo is faster than a 2.4GHz Core 2 Duo. Performance varies according to many factors, clock speed is just one.
E8400 is just the model number. An E8500 is slightly faster (in clock speed and actual performance) than an E8400, and an E8200 is slightly slower. Bigger numbers are often, but not always better; and again only when comparing processors of the same family.
Wolfdale, Yorkfield and Kentsfield are the codenames for a particular processor line. Wolfdale is the 45nm dual cores, Yorkfield is the 45nm quad cores, Kentsfield is the 65nm quad cores.
I don't know how to explain manufacturing process in a highly simplified form, so I'll let someone else do that
45nm or 65nm technology is how fine a resolution they can etch into the silicon.
It is the width of the electrical pathways in the CPU. The smaller the width the more transistors etc. they can pack into the same space (CPU). They usually add a few more (millions) transistors and reduce the overall size of the CPU die. The transistors add more features MMX SSE SSE2 etc. Reducing the size means that the distance a signal has to travel is smaller and the thermal mass of the die reduces too. This means that you can run faster and cooler, corresponding to increased clock rate.
This is only a generalisation but hopefully you get the idea.