If you think of a perfect Doji candle, where the wicks on top and bottom are exactly the same, that's a candle with a delta of 0. What this indicator does is show the delta/difference between wicks, if the top wick is longer than the bottom wick it shows sell pressure/bear interest, which is displayed as a red bar and vice versa for buy/bull pressure, which is shown as green bars. I added arrows for clarity.
It's a different way of visualizing wicks, which can clarify sentiment and be a useful way to understand wicks better in general. One way to use it is to look for clusters of 3/4 larger bars in a row, which generally helps to determine future direction, especially when seen at important levels.
