Button debouncing
A button is a simple device; when we push it, it gives a value, otherwise it gives another value. Unfortunately, it is not always like that. When we push or release a button, for a very small amount of time the button bounces between pushed or not. This is due to mechanical errors and wear and tear in the button.
Even if it is a small amount of time, the Arduino is quick, and when we press the button, it may read values that are quickly bouncing between pressed and not pressed. In most cases, this is not a problem; but in many cases, this happens and it can take hours to detect what is going wrong. Better be safe than sorry!
Another very important application of this is reading a button only once. When we press the button, we keep it pressed for a few milliseconds. In this time, the Arduino can read it hundreds, even thousands of times. It detects a few hundred times instead of once that we pushed the button. This is the primary use of debouncing in the Arduino world.
