All arithmetical and logical functions within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware component is sometimes called the "brains" of the computer also. The rate at which the CPU runs system instructions is also referred to as its speed and it's measured in Hertz. The swifter the processing unit is, the more quickly scripts and web apps will be executed, even 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 connection, and many others. All modern CPUs have a number of cores, which work together. As a result, the effectiveness and the workload which a CPU can tackle increase, because each core can process several tasks individually and several cores can handle a single task which can't be processed by a single core.