Commonly abbreviated as RSI.

Is a momentum indicator.

Was developed by Welles Wilder.

Is computed using close prices.

Returns one time series, which is the ratio of 14-period exponential moving averages for gains and losses rescaled to be between 0 and 100.

FinancialIndicator["RelativeStrengthIndex",n] uses a period-n moving average. The first value in the time series occurs after periods.