Volume shows the number of securities that are traded over a particular time. Higher volume indicates higher degree of intensity or pressure.Being one of the most important factors in trade it is always analyzed and estimated by chartists. In order to determine the upward or downward movement of the volume, they look at the trading volume gistograms usually presented at the bottom of the chart. Any price movement is of more significance if accompanied by a relatively high volume than if accompanied by a weak volume.
By viewing the trend and volume together, technicians use two different tools to measure the pressure. If prices are trending higher, it becomes obvious that there is more buying than selling pressure. If the volume starts to decrease during an uptrend, it signals that the upward trend is about to end.
As mentioned by Forex analyst Huzefa Hamid "volume is the gas in the tank of the trading machine". Though most traders give preference only to technical charts and indicators to make trading decisions, volume is required to move the market. However, not all volume types may influence the trade, it’s the volume of large amounts of money that is traded within the same day and greatly affects the market.