All arithmetical and logical functions in a computer/server configuration are tackled by its Central Processing Unit, or CPU. This hardware part is typically called the "brains" of the computer system as well. The rate at which the CPU executes system instructions is usually referred to as its speed which is measured in Hertz. The speedier the processing unit is, the more quickly scripts and web programs will be executed, even though the efficiency of the latter is determined by other things also - the read/write speed of the hard disk, the amount of physical memory, the network connection, etc. All new CPUs have multiple cores, that work together. For that reason, the functionality and the workload which a CPU can tackle increase, since each core can process various tasks separately and a number of cores can handle a single task which cannot be processed by one core.