What is a finger pop?

A finger pop is a popping noise produced using the fingers. It can be achieved by several techniques, but often involves moving one finger rapidly off another, creating a vacuum as the skin on the lower finger is suddenly released, causing the popping noise. Other methods like pressing the thumb's nail into the first finger's nail (nail pop), or by pulling down the curled index and middle fingers with one hand and the tip of the thumb of the other hand, which creates a popping noise as they're released (knuckles pop).