It is NOT the same as "relative strength". Relative strength is a comparison of price action between two complete different sets of prices. For example, you might measure the relative strength of Apple stock against the S&P 500 market index.
As you'll see below, RSI is based on the price action for only one set of prices. So both Ford and the S&P500 have their own, unique relative strength index.
Chart courtesy of Stockcharts.com
Safe Investing Tip:
RSI developed by J. Welles Wilder, and made its first appearance in the June 1978 equivalent of today's Futures Magazine!
Traditionally, RSI readings above 70 indicate an "overbought" condition. Readings under 30 indicate and "oversold" condition.
RSI = 100 - (100 / (1 + Relative Strength Factor))
The relative strength factor is the average increase in price on up days, divided by the average decrease in price on down days.
After all, you probably don't buy something without reading several reviews...why should buying and selling assets be any different?