There is relative strength vs. an index, usually the S&P 500. The relative strength of the index is set to 100 or 1, depending on the software you use, so that it is the standard by which your stock is being judged. If your stocks' relative strength number is above that then it is stronger than the index. Relative strength and the 200 day moving average are the most common technical indicators used by swing and position traders, although there are many more.
Wilders RSI is completely different. It is an oscillator. Many people prefer using the stochastic as an oscillator. If you aren't familiar ith oscillators there is a good book called "trading with oscillators".