All arithmetical and logical functions within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware element is typically called the "brains" of the PC also. The rate at which the CPU completes system instructions is generally referred to as its speed and it is measured in Hertz. The swifter the processing unit is, the more quickly scripts and web apps will be executed, even though the overall performance of the latter is dependent upon other things too - the read/write speed of the hard drive, the amount of physical memory, the network connectivity, etc. All current CPUs have several cores, that work together. Thus, the effectiveness and the workload a CPU can handle increase, since each and every core can process a number of tasks separately and numerous cores can handle 1 task which can't be processed by 1 core.