All arithmetical and logical operations in a computer/server configuration are tackled by its Central Processing Unit, or CPU. This hardware component is oftentimes called the "brains" of the personal computer as well. The rate at which the CPU completes system instructions is typically referred to as its speed and it's measured in Hertz. The swifter the processing unit is, the quicker scripts and web apps shall be executed, though the performance of the latter is dependent upon other things too - the read/write speed of the hard drive, the amount of physical memory, the network connectivity, etc. All modern CPUs have a number of cores, that work together. Because of this, the overall performance and the workload a CPU can handle increase, because every core can process several tasks separately and a number of cores can handle 1 task which can't be processed by one core.