It gives you the ratio between the of the last x days and the of the last y days.
---> ROC-ATR Ratio = /ATR
Therefore, you can see how much the price has moved relative to the prices in the past.
This is important because (in my opinion) the basic indicator is not very meaningful if you don't look at the average of recent history.
For example, a of 5% over the last 3 days might be very high for Forex but very small for some crypto.
Consequently, this indicator makes it possible to compare (and be used on) every instrument in every industry the same way.
Generally speaking, it makes more sense if the ATR length is larger than the length.
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.