This document discusses timers and how they are used to count time in digital hardware. Timers use counters and prescalars to determine the time interval for an overflow interrupt. A timer overflow can be used to trigger an action every specific time period. The document explains counters, prescalars, and how to calculate the number of counts and time to overflow for a timer. It provides an example of using the 8-bit Timer0 peripheral in a microcontroller to generate an interrupt every 4 seconds using a 32.768 kHz oscillator. Real-time applications of timers are discussed, along with an assignment to generate a 100 kHz square wave using Timer0.