Imagine many people wanting to buy bitcoin. Would this generate huge trading volume? correct? now as there are many buyers. they are attacking the sellers. what I mean to say. the price starts to rise because there are many more buyers than sellers at the price level. consequently you will have a large trading volume on bullish candles. because there were many negotiations, with many more buyers than sellers in that period of time. Do you understand the importance of volume? volume validates price movement. movement without volume is pullback.
