All arithmetical and logical procedures inside a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware element is usually called the "brains" of the PC also. The rate at which the CPU runs system instructions is typically referred to as its speed and it's measured in Hertz. The faster the processing unit is, the faster scripts and web apps will be executed, although the general performance of the latter depends on other things as well - the read/write speed of the hard drive, the amount of physical memory, the network connectivity, etc. All newer CPUs have several cores, which work together. Therefore, the overall performance and the workload a CPU can manage increase, as each and every core can process a number of tasks separately and several cores can handle 1 task that can't be processed by a single core.