I'm a little surprised I couldn't find a BB crossover script on here since I've always used it on other charting software. So of course I had to write one in for TradingView.
Essentially what this script signifies are price breakouts when price crosses over the upper BB band. So what it shows is that market conditions are entering overbought territory.
Length is set to 20 and Standard Deviation is set to 2. These are the default settings.
The way I use the script is to identify breakouts in price, as well as a signal to start scaling out of a position if I am already in one.