A three-candle imbalance where the wicks do not overlap — price often returns later to fill it.
A Fair Value Gap forms when three consecutive candles align so that the first candle's high and the third candle's low do not overlap (or vice versa for a short FVG). The result is an empty price region across the middle candle. In the ICT / smart-money tradition these gaps are treated as imbalances the market wants to rebalance — price often returns to fill them. A filled FVG frequently becomes the entry for a trend continuation.
EUR/USD H1: a sharp rally leaves an FVG between 1.0840 and 1.0852. Two days later the zone is sold into, filled, and the long trend resumes.