The Kijun Sen Envelope Indicator is a popular and free Forex indicator that is useful for traders of all levels. It works by plotting two envelopes around the Kijun Sen line, which is a moving average of the highest high and lowest low price over a certain period of time. The envelopes are set at a certain percentage above and below the Kijun Sen line. When the price breaks out of either envelope, it can signal a trend reversal or breakout. It is a useful tool for traders looking to capitalize on short-term price movements.