A computer processor or CPU (central processing unit) speed is determined by the clock cycle, which is the time between two pulses of an oscillator. Generally, the higher number of pulses per second, the faster the computer processor can to process information. The clock speed is measured in Hz, often either MHz (megahertz) or GHz (gigahertz). For example, a 4 GHz processor performs 4,000,000,000 clock cycles per second.
Computer processors can execute one or more instructions per clock cycle, depending on the type of processor. Early computer processors and slower CPUs can only execute one instruction per clock cycle, but modern processors can execute multiple instructions per clock cycle.