All arithmetical and logical operations within a computer/server configuration are handled by its Central Processing Unit, or CPU. This hardware element is oftentimes called the "brains" of the PC also. The pace at which the CPU runs system instructions is generally referred to as its speed and it's measured in Hertz. The speedier the processing unit is, the speedier scripts and web applications shall be executed, although the performance of the latter depends upon other things as well - the read/write speed of the hard disk, the amount of physical memory, the network connection, etc. All modern CPUs have a number of cores, that work together. Therefore, the functionality and the workload which a CPU can manage increase, as every core can process several tasks independently and a number of cores can handle a single task which cannot be processed by 1 core.