You have said it right buy low sell high. But it is not the short term investment. You have to wait for the right time to buy then wait till the price gets high then you sell it. "Buy low, sell high" is misleading in some ways, as lows and highs only become clear in retrospect. There is always a bull who considers a stock price to be low and a bear who considers it high. Often, both sides make compelling arguments. The challenge for investors and traders is to determine which stocks are being driven to extremes by fundamentals and which are being driven by emotions. Mean-reversion strategies are more likely to work when price moves are driven by emotions.