A candlestick summarises one interval of trading with four prices. The body spans the open and the close; the thin lines above and below — wicks or shadows — reach the high and the low. Convention colours the body one way when the close was above the open and another when it was below, so direction is legible without reading the axis. Change the interval and each candle covers more or less time; the notation is identical whether one candle is a minute or a week.
The information is in the proportions. A long body with short wicks says the period trended and closed near its extreme. A short body with long wicks in both directions says the price travelled a long way and finished where it started, which is indecision rather than calm. A long lower wick says sellers pushed the price down and buyers took it back before the close. Reading the shape is reading the balance between the two sides over that interval.
Named patterns are combinations of these shapes. A doji is a candle that opens and closes at nearly the same price. A hammer is a small body sitting on a long lower wick after a decline. Engulfing patterns are candles whose body completely covers the previous one. These names are a vocabulary for describing what has already happened, and that is their honest use.
Their predictive record is another matter. Where patterns have been tested systematically across large samples, most perform close to chance once trading costs are included, and their apparent success in illustrations owes a great deal to hindsight — the examples chosen are the ones that worked. A pattern that appears at a level the market has already reacted to, on volume that confirms participation, is a more interesting observation than the same pattern in the middle of a range. Context is doing the work.
Two mechanical points cause real confusion. Cryptocurrency trades continuously, so there is no session open or close: a daily candle closes at whatever hour the data provider treats as midnight, and different providers use different ones. Two charts of the same asset can therefore show different daily candles. Second, the candle at the right-hand edge is still forming. Its body and wicks will change until the interval ends, and reading a pattern into an unfinished candle is reading a pattern into an incomplete sentence.
The reasonable use of candlesticks is as a compact record. They compress a great deal of information into a form the eye reads quickly, they make ranges and rejections visible, and they are the shared notation of everyone discussing a chart. What they do not contain is information about the future, and no amount of pattern naming puts it there.