The Absolute Price Oscillator (APO) calculates and displays the difference between two Exponential Moving Averages with different periods value of an instrument price and is expressed as an absolute value.
When the Absolute Price Oscillator (APO) is crossing above zero is considered bullish, when the Absolute Price Oscillator (APO) is crossing  below zero is considered bearish.
The Absolute Price Oscillator (APO) formula or calculation is APO = Fast Exponential Moving Average - Slow Exponential Moving Average,
The Fast Exponential Moving Average is Shorter Period EMA and the Slow Exponential Moving Average is Longer Period EMA.