What is a computer's clock speed?

Clock speed refers to the number of pulses per second generated by an oscillator that sets the tempo for the processor (Whatis.com). It is the speed at which a microprocessor executes instructions (Webopedia). The clock itself is actually a quartz crystal that vibrates at a certain frequency when electricity is passed through it. Each vibration sends out a pulse or beat, like a metronome, to each component that's synchronized with it (Clock Speed - PC ComputerNotes). For our purposes, it means is "how quickly we change the electronic switches from one state to another"