
First we begin with some theoretical stuff: there are two kinds of Volume we can put on our charts - Real or Tick Volume.
Real volume shows the actuall currency/stock/metal exchanged for the period of a particular bar, Tick Volume shows the number of price changes for the period, which is approximately the number of trades made. Some platforms take in account two consecutive ticks at the same price as one and that is where the 'aproximate' part comes from. In Forex of CFD markets real volume is not available, at least for us poor retail traders. Real and Tick volume are not the same, but there is a connection between them - the more trades made the more volume exchanged. In most cases that is more than enough for technical analysis.