Wick
The thin lines above and below a candle's real body, marking the session's high and low extremes beyond the open/close range.
Wicks (also called shadows or tails) extend from the real body to the session high (upper wick) and low (lower wick). They record prices that were visited but rejected — areas where the opposing side pushed back.
A long lower wick shows sellers drove price down but buyers recovered it — bullish pressure. A long upper wick shows buyers pushed high but were rejected — bearish pressure. Wick length relative to body size is the defining feature of hammers, shooting stars, and pin bars.