All arithmetical and logical functions within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware component is occasionally called the "brains" of the PC as well. The rate at which the CPU executes system instructions is generally referred to as its speed and it's measured in Hertz. The faster the processing unit is, the more quickly scripts and web applications will be executed, even though the general performance of the latter is determined by other things also - the read/write speed of the hard disk, the amount of physical memory, the network connectivity, etc. All current CPUs have numerous cores, which work together. Thus, the overall performance and the workload that a CPU can tackle increase, because every core can process several tasks independently and a number of cores can handle a single task which can't be processed by one core.
