What the candlestick chart does not show

A candle sums up a period in four prices: the open, the high, the low and the close. Sometimes the total volume is added. It is useful, but it is a summary. Two perfectly identical candles can tell two opposite stories, and the story is precisely what interests the trader.

Classic indicators change nothing: a moving average, an RSI or a MACD are calculated from price. They smooth it and lag it, they add no new information. Order flow goes looking for the source data: the orders themselves.