All arithmetical and logical functions inside a computer/server configuration are handled by its Central Processing Unit, or CPU. This hardware component is usually called the "brains" of the computer also. The pace at which the CPU completes system instructions is usually referred to as its speed and it's measured in Hertz. The swifter the processing unit is, the quicker scripts and web programs will be executed, although the performance of the latter is determined by other things too - the read/write speed of the hard disk, the amount of physical memory, the network connection, and many others. All modern CPUs have several cores, which work together. For that reason, the efficiency and the workload which a CPU can take care of increase, since each core can process various tasks separately and numerous cores can handle a single task which cannot be processed by one core.