It is the popular RSI indicator with VWAP as a source instead of close.
What is the Volume Weighted Average Price (VWAP)?
VWAP is calculated by adding up the dollars traded for every transaction (price multiplied by the number of shares traded) and then dividing by the total shares traded. That is, volume.
On the Backtest, trades are laddered to improve the average entrance price.
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.