Volume

Volume measures the “worth” of a market move. If a currency pair has a strong price move either up or down, the perceived strength of that move depends on the amount of volume for that period. Moves backed by higher volume are more significant. By monitoring volume, a trader should not be left behind on important market moves. Important moves will usually come on a spike, or a short period of time when there is more volume than normal. Volume can help a trader prepare for breakout from a trend. Traders should also be able to identify periods where there are calm ranges and consolidation as they will have lower volume.
Consider the figure below:

Figure 1 – Examples of movements on higher volume; and sideways price action on lower volume.