A Hammer candlestick pattern is a single candlestick pattern that typically appears at the end of a downtrend and signals a potential reversal in price direction. Visually, a Hammer candlestick consists of a small body near the top of the candlestick's range with a long lower shadow, and in some cases, little to no upper shadow. This formation resembles a hammer, hence the name.

The distinguishing feature of a Hammer candlestick is its long lower shadow, which represents the distance between the low of the candlestick and the opening or closing price. The body of the candlestick is usually small, signifying minimal price movement between the open and close. However, the presence of a small body is not a strict requirement for a candlestick to be considered a Hammer; it's primarily characterized by the long lower shadow.

On a price chart, a Hammer candlestick typically stands out among surrounding candlesticks due to its unique shape and the contrast between its small body and long lower shadow. Traders often interpret this pattern as a sign that sellers were initially in control, driving prices lower during the trading session, but were later overwhelmed by buyers, resulting in a strong bullish reversal. As such, the appearance of a Hammer candlestick can be a significant signal for traders to watch for potential bullish opportunities in the market.