All arithmetical and logical functions within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware element is typically called the "brains" of the computer system also. The pace at which the CPU runs system instructions is generally referred to as its speed and it's measured in Hertz. The swifter the processing unit is, the speedier scripts and web apps will be executed, even though the general performance of the latter depends upon other things as well - the read/write speed of the hard drive, the amount of physical memory, the network connectivity, etc. All new CPUs have several cores, that work together. Thus, the effectiveness and the workload which a CPU can tackle increase, as every single core can process a number of tasks individually and a number of cores can handle one task which can't be processed by a single core.