The equivolume analysis gives different information about price range and volume at the same time in order to underline different market situations. Equivolume chart construction is very specific, volume display is not anymore at bottom of the chart (where it is normally displayed in any bar chart) and it is included into price representation. Let's have a look at a bar chart.
The x-axes represent time, while the y-axes represent price. Every bar in the x-axes represent the volume of the exchanges during a market session, independently from the number of the exchanges. Time measures market evolution, in fact price moves only according to time and regardless the number of exchanges. Let's have a look now at the same chart, but with the equivolume construction.
In equivolume chart closing price is not displayed as Arms (the developer of this kind of chart) doesn't consider this a useful information for market study. Differently from a bar chart, the aim is to reach a volume scale that clearly represent stock movements: session with few volumes are showed with small rectangles (the base is small compared to the height), while the big volume session are emphasized with a rectangle that has a large base.
Using this kind of chart we must be careful because a mistake in the volume scale might lead to the formation of very similar rectangles that don't clearly show, from a graphic point of view, the main aspect that this methodology wants to express.