The Relative Strength Indicator is used to see if assets are overbought or oversold. A score above 70 means the purchase is overbought, and one below 30 means it is oversold. However, you must remember not to make a hasty decision and wait for the indicator to rise more than 70, drop more than 30 and rise again before you buy.
Another use of RSI is resistance and support levels. During an uptrend, a stock will hold   above 30 and reach 70 or above often. During a downtrend, the stock will hold below 70 and reach 30 or below often.