A stochastic is an oscillator that measures overbought and oversold conditions in the market.
Stochastics tells us when the market is overbought or oversold. Stochastics are scaled from 0 to 100. When the stochastic lines are above 80 (the red dotted line in the chart above), then it means the market is overbought. When the stochastic lines are below 20 (the blue dotted line), then it means that the market is oversold. As a rule of thumb, we buy when the market is oversold, and we sell when the market is overbought.