Four prices, one defined trading period
The open is the first relevant price and the close is the last under the data provider’s session definition. The high and low are the extremes within that same period. A completed daily candle and a completed weekly candle summarize different intervals. Weekly open and close come from the beginning and end of that week, not from averaging daily values.
The body size is the absolute difference between open and close. The upper shadow extends from the larger of those two prices to the high; the lower shadow extends from the smaller to the low. Colors are display conventions, so check whether the software colors candles by open-to-close direction or another comparison.
One candle, two possible price paths
Assume a completed candle has open 100, high 108, low 97 and close 106 dollars. Its range is 11 dollars, its body is 6, its upper shadow is 2 and its lower shadow is 3. The open-to-close increase is 6%. Price might have fallen to 97 before rising to 108, or reached 108 before falling to 97 and recovering. Both paths can produce the same OHLC. The candle alone cannot establish which threshold was reached first.
A green body does not necessarily mean a gain from yesterday
If the previous close was 110, the example’s 106 close is down 4 dollars from the prior session despite being above its own open. Gaps make this distinction especially useful. Splits, dividend adjustments, missing transactions and different session boundaries can also change apparent candle relationships. Compare data prepared on the same basis.
Translate the picture back into numbers
On an available completed daily, weekly or monthly chart, read the four values and reconstruct body and shadows. Compare the close both with the open and with the previous close. Before discussing a reversal or a broken level, confirm the candle is finished and specify the timeframe. Avoid claiming a precise intraperiod sequence from OHLC alone.
Primary sources
Sources explain the mechanics and limitations; the editorial examples use invented numbers rather than market quotations.
Your next practical step
Open a completed-candle chart and verify its shape using the underlying OHLC values.
Open the first-chart instructions ↗