The engulfing pattern is made up of an initial smaller candle and a larger second that engulfs the first. Typically engulfing patterns are seen as trend reversal patterns when the first candle is bearish, then the second is a larger bullish bar.
Engulfing patterns depict not only trends ending, but that momentum into the opposite direction is building fast. A strong engulfing candle indicates a more meaningful signal is typically on the horizon.