Judging by the code of indicator, it calculates the difference between the maximum maximums and minimum minimums of prices of the candlesticks for the last 20 bars (parameter).
The result is displayed in points.
extern int N=20; // period of the channel
The Acceleration/Deceleration Indicator (AC) measures acceleration and deceleration of the current driving force.Average Directional Movement Index (ADX)
The Average Directional Movement Index Indicator (ADX) helps to determine if there is a price trend.