All arithmetical and logical operations within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware part is usually called the "brains" of the PC as well. The pace at which the CPU carries out system instructions is commonly referred to as its speed and it is measured in Hertz. The faster the processing unit is, the faster scripts and web apps will be executed, though the overall performance of the latter is determined by other things as well - the read/write speed of the hard disk drive, the amount of physical memory, the network connection, etc. All new CPUs have multiple cores, which work together. Because of this, the overall performance and the workload that a CPU can tackle increase, because every core can process a number of tasks independently and a number of cores can handle one task that cannot be processed by 1 core.