Volume is "the blood" of a stock, without volume, a stock never has enough strength to move. Strong volume means strong positive money flow into the stock with large net buying volume transaction. If a stock had an ONE-day strong volume transaction, after that day, the volume is no longer expanding. That is more likely price will come down soon within 10 days. Multiple days of high volume transactions are a very good sign of strong accumulation which indicates the strong move is on the way. It is better for investors to choose high volume stocks to trade due to liquidity issue.
OBV rises when volume on up days outpaces volume on down days. OBV falls when volume on down days is stronger. A rising OBV reflects positive volume pressure that can lead to higher prices.