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.
The basic idea is that he says a very effective filter for all your trading is to only take trades long when the bar closes in top 25% of range and above 50DMA. And then the opposite for below. Makes sense as this keeps you in trades with the trend at hand.