All arithmetical and logical functions in a computer/server configuration are handled by its Central Processing Unit, or CPU. This hardware component is sometimes called the "brains" of the computer too. The pace at which the CPU completes system instructions is generally referred to as its speed and it's measured in Hertz. The quicker the processing unit is, the more quickly scripts and web apps will be executed, even though the general performance of the latter is determined by other things too - the read/write speed of the hard drive, the amount of physical memory, the network connectivity, etc. All new CPUs have multiple cores, that work together. Thus, the functionality and the workload a CPU can take care of increase, since each core can process different tasks individually and a number of cores can handle one task that can't be processed by a single core.