A prescaler is a device used in a microcontroller to divide the frequency of the clock signal that is input to the microcontroller. The prescaler can be used to divide the frequency by any integer value between two and 65536. The prescaler can be used to slow down the clock speed of the microcontroller, allowing it to operate at slower speeds. This can be useful if the microcontroller is operating too fast and the system needs to be slowed down to ensure the accuracy of processor operations. Prescalers can also be used to boost the speed of the microcontroller if the system requires faster processing.