All arithmetical and logical functions in a computer/server configuration are tackled by its Central Processing Unit, or CPU. This hardware element is oftentimes called the "brains" of the computer also. The rate at which the CPU carries out system instructions is typically referred to as its speed and it's measured in Hertz. The faster the processing unit is, the speedier scripts and web apps will be executed, though the performance of the latter depends upon other things as well - the read/write speed of the hard disk drive, the amount of physical memory, the network connectivity, etc. All modern CPUs have multiple cores, which work together. Because of this, the effectiveness and the workload a CPU can handle increase, due to the fact that every core can process different tasks individually and numerous cores can handle 1 task which cannot be processed by 1 core.