Dow theory is used to determine the trend of a market, but not for deciding which stocks to sell and buy, dow theory was put forward by Charles h dow. Dow theory uses the higher bottoms and higher tops to derive trend. If HB AND HT are formed, it’s Bullish and LT-LB are formed it’s bearish. Both of them have to accompanied with a good amount of volume, which signifies the amount bought and sold. Demand> Supply it’s known as bullish, and if Supply> demand, its known as bearish.