I often hear that the means overbought and oversold which is simply an unnuanced explination.
The is a momentum indicator: .
When the reaches overbought zone price will more often than not extend lower beyond that point. What you want to look for on the shorter timeframes is divergences between price and momentum.
Needless to say an indicator alone will not make you a profitable trader. The real playout is hindsight and as a trader we have to make bets based on our analysis and more importantly manage our risk well.