All arithmetical and logical operations within a computer/server configuration are tackled by its Central Processing Unit, or CPU. This hardware part is usually called the "brains" of the computer too. The rate at which the CPU carries out system instructions is usually referred to as its speed which is measured in Hertz. The quicker the processing unit is, the more quickly scripts and web apps will be executed, although the performance of the latter is determined by other things also - the read/write speed of the hard disk drive, the amount of physical memory, the network connection, and so on. All current CPUs have several cores, which work together. Because of this, the effectiveness and the workload a CPU can take care of increase, as each core can process a number of tasks independently and several cores can handle 1 task that can't be processed by a single core.