This is the classic OBV (On-Balance Volume) formula modified to evaluate OBV state based on a moving average. OBV is a momentum indicator that uses volume flow to predict changes in asset price. While I am not an expert on OBV, my thesis for the logic conditions I have implemented follow fairly standard confirmation/invalidation logic used in many other indicators. I use the below icons across many of my scripts to evaluate bar state and to help confirm current conditions in a trade.