The columns bars show how far each candlestick's close price is to the midpoint of its high and low. It's possible for the column bar to be a different color than the candlestick itself if the close was above or below the midpoint. An average line is shown that takes the average of a given length amount of column bars. There is an option to show the absolute value only of the columns and the average line.
This is based on an idea I found about candlestick range bars implying volume. This is an attempt to put that theory into practice and to see if there's any truth to it. It's not exactly volume and may not always look like it, and it does not show how many trades took place but instead tries to use price in relation to the high and low range.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.