The Stochastic Oscillator is a momentum indicator used in technical analysis to identify overbought and oversold market conditions. It oscillates between 0 and 100, with readings above 80 indicating overbought conditions and readings below 20 suggesting oversold conditions.

The Stochastic Oscillator is calculated by comparing the current closing price to the range of prices over a specified time period, typically 14 periods, to determine the relative position of the current closing price within that range. The formula for the %K line of the Stochastic Oscillator is: %K = [(Current Close - Lowest Low) / (Highest High - Lowest Low)] * 100. %K is known as the fast stochastic indicator. The "slow" stochastic indicator is known as %D and is a 3-period moving average of %K.

Traders can use the Stochastic Oscillator to generate potential buy and sell signals. When the indicator crosses above 80, it suggests that the market may be overbought and could be due for a correction, signaling a potential sell opportunity. Conversely, when the indicator crosses below 20, it indicates oversold conditions, suggesting that the market may be oversold and could be poised for a reversal to the upside, signaling a potential buy opportunity. 

The Stochastic Oscillator has several variations. One of them is the Full Stochastic Oscillator, which uses the highest high and lowest low over a specified period, in addition to the closing price, to calculate its values. This variation provides a smoother indicator line and can offer more accurate signals compared to the traditional Stochastic Oscillator. 

Another variation is the Slow Stochastic Oscillator, which applies a moving average to the %K line, resulting in a slower and less responsive indicator. This variation is less prone to false signals but may lag behind market movements compared to the traditional Stochastic Oscillator.

Learn more: 5 Essential Indicators Used in Technical Analysis.