J. Welles Wilder, in *New Concepts in Technical Trading Systems* (1978) — the book that introduced the Relative Strength Index, Average True Range, ADX, Parabolic SAR, and the Directional Movement Index in a single volume — wrote that the goal of any technical indicator is 'to provide a momentary glimpse of the equilibrium point in any market, and to tell us whether the most recent equilibrium point is above or below the previous equilibrium point.' Indicators are not predictions; they are summaries of what price has already done, condensed into a number or a curve that makes specific structural features (trend direction, momentum exhaustion, volatility regime) easier to read than the raw chart.

There are hundreds of indicators in the technical-analysis literature; most professionals focus on just a few. This lesson covers the two that have earned their place: simple moving averages, which summarize trend direction across a chosen window; and the Relative Strength Index, which summarizes the momentum balance between rising and falling closes.