Piercing is a two-candle bullish reversal candlestick pattern found in a downtrend. The first candle is red and has a larger than average body. The second candle is green and opens below the low of the prior candle, creating a gap, and then closes above the midpoint of the first candle.
The pattern shows a possible shift in the momentum from the downside to the upside, indicating that a reversal might happen soon.