The On Balance Volume indicator (OBV) is used 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. OBV is primarily used to confirm or identify overall price Trends or to anticipate price movements after Divergences.
In addition to OBV, EMA and SMA are included. the EMA is used for Support and Resistances for the OBV. and the SMA is used by its Slope (can be S/R as well).