The Processor or CPU (Central processing unit) is commonly referred to as the "brains" of the computer, even though this is only partially true since a real brain performs many functions including thinking (processing), issuing commands and storing information (short and long term memory) .
On a computer, the "short term memory" is stored in RAM or Random access memory and the "long term memory" is stored on the Hard disk drive.
The job of the CPU is to retrieve data from memory, to process this information and then to issue commands to the system based on this information, the CPU is the computer's top manager (the boss).
Speed (clock speed) is crucial to performance, since the faster the boss is able to issue the commands, the faster the system performs. Speed is measured in Hertz, or cycles per second. Today's processors operates at thousands of millions (1, 000, 000, 000) of cycles per second (Giga Hertz or just GHz).
Performance and speed
The performance of a processor is no longer based on CPU speed alone, other factors impact on performance; it is essential to look at performance charts rather than looking at CPU speeds before making a decision.
Dual core and quad core
A dual core processor has two physical processor cores in a single chip, and theoretically should deliver twice the performance of a single core CPU when running multi-threaded applications.
Quad core processors have four processors in a single chip. Performance, in theory, should be twice that of a dual core.
Gaming (at the moment) - games are not multi-threading - they do not use 4 cores, they mainly use a single core, and sometimes they use two cores. If you are a gamer, it is recommended keeping up with the latest information from other Internet users, and to buy accordingly.
Cache (pronounced cash) also impacts on performance, this is the amount of information a CPU is capable of "remembering" before it has to get the information again (lets call it very short term memory that will be forgotten eventually as the boss gets more work to do - it is something the boss knows at that specific time). The more cache a CPU has, the better it performs.