Heiken Ashi, in Japanese = “average bar”. The standard candlestick uses open, high, low, close price values over the same time period. With Heiken Ashi, previous time periods enter the calculation to provide a modified candlestick. See the chart below of a downtrend…

Calculation
Current Average Price: *Close = (Open + High + Low + Close) / 4

Previous Midpoint: *Open = [*Open(Previous) + Close(Previous)]/2

Maximum value: *High = Maximum (High, *Open, *Close)

Minimum value: *Low = Minimum (Low, *Open, *Close)

Otherwise, all the same chart patterns can be applied to Heiken Ashi candlesticks - giving a smoother picture. Probably more used in commodities and equities than in forex trading - although some forex traders do use Heiken Ashi bars for calculating exit strategies.