All arithmetical and logical functions within a computer/server configuration are handled 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 executes system instructions is commonly referred to as its speed and it's measured in Hertz. The quicker the processing unit is, the quicker scripts and web apps shall be executed, even though the performance of the latter is dependent upon other things also - the read/write speed of the hard disk, the amount of physical memory, the network connectivity, and so forth. All new CPUs have a number of cores, that work together. Therefore, the overall performance and the workload which a CPU can tackle increase, because each and every core can process a number of tasks separately and a number of cores can handle 1 task which cannot be processed by a single core.