PWM or Pulse Width Modulation is a variation of how much time the signal is high in an analog fashion. The signal can be high or low, and the user can even change the proportion of the time.
PWM is a way to control analog devices with a digital output. Another way to put it is that you can output a modulating signal from a digital device such as an MCU to drive an analog device. It’s one of the primary means by which MCUs drive analog devices like variable-speed motors, dimmable lights, actuators, and speakers. PWM is not true analog output, however. PWM “fakes” an analog-like result by applying power in pulses, or short bursts of regulated voltage.
An example would be to apply full voltage to a motor or lamp for fractions of a second or pulse the voltage to the motor at intervals that made the motor or lamp do what you wanted it to do. In reality, the voltage is being applied and then removed many times in an interval, but what you experience is an analog-like response. If you have ever jogged a box fan by applying power intermittently, you will experience a PWM response. The fan and its motor do not stop instantly due to inertia, and so by the time you re-apply power it has only slowed a bit.
