The On Balance Volume indicator (OBV) is used in technical analysis to measure buying and selling pressure. It is a cumulative indicator meaning that on days where price went up, that day's volume is added to the cumulative OBV total. If price went down, then that day's volume is subtracted from the OBV total. The OBV value is then plotted as a line for easy interpretation. On Balance volume is primarily used to confirm or identify overall price trends or to anticipate price movements after divergences.
Read more about the On Balance Volume indicator
in TradingView wiki.