Volume is the number of shares of a particular stock or group of stocks that are traded over a given time period. Many traders will only trade stocks with high volume, as the execution they receive on these stocks is generally better than in low volume stocks. Many traders will also use volume as a part of their analysis, giving more credence to moves in the market which are accompanied by higher volume, as this generally means that there is more participation in the move than if this were not the case.