A candlestick chart (also called Japanese candlestick chart) is a style of financial chart used to describe price movements of a security, derivative, or currency. Each "candlestick" typically shows one day; so for example a one-month chart may show the 20 trading days as 20 "candlesticks".
It is like a combination of line-chart and a bar-chart: each bar represents all four important pieces of information for that day: the open, the close, the high and the low. Being densely packed with information, they tend to represent trading patterns over short periods of time, often a few days or a few trading sessions.
Candlestick charts are most often used in technical analysis of equity and currency price patterns. They appear superficially similar to box plots, but are unrelated.
Heikin-Ashi (平均足, Japanese for 'average bar') candlesticks are a weighted version of candlesticks calculated with the following formula:
Close = (open + high + low + close) / 4
High = maximum of high, open, or close (whichever is highest)
Low = minimum of low, open, or close (whichever is lowest)
Open = (open of previous bar + close of previous bar) / 2
Heikin-Ashi candlesticks must be used with caution with regards to the price as the body doesn't necessarily sync up with the actual open/close. Unlike with regular candlesticks, a long wick shows more strength, whereas the same period on a standard chart might show a long body with little or no wick. Depending on the software or user preference, Heikin-Ashi may be used to chart the price (instead of line, bar, or candlestick), as an indicator overlaid on a regular chart, or as an indicator plotted on a separate window.