The Stop-loss is calculated at the current close price minus 1x ATR and is plotted as a red line by default.
The Take-profit is calculated at the current close price plus 1.5x ATR and is plotted as a green line by default.
The colors for each line can be changed, as well as the default ATR values (length, smoothing).
When you see a long or short signal (your own preference), enter your position and set your take-profit and stop-loss limits at the current red/green lines, based on whatever Risk-Reward you've set it to.
This is also helpful in determining whether or not a trade offers enough potential to risk prior to entering the trade.
When the lines are far apart, the ATR is high. When the lines are close together, the ATR is low. This can be used to determine and allow traders to buy during consolidation and sell into strength.
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.