The document discusses the Relative Strength Index (RSI) technical indicator. It explains that RSI is used to identify overbought and oversold zones of a stock to find buying opportunities in oversold zones below 40 and selling opportunities in overbought zones above 60. However, during strong trends, RSI may remain in one zone for an extended period. Divergences, where the price and RSI move in opposite directions, can also be used to identify trading opportunities, such as a bullish divergence in an oversold zone signaling a potential upward move.