A doji is a candlestick in which the open and close finish at virtually the same price, producing a body so small it looks like a cross or line with wicks on either side. It marks a moment of equilibrium: price travelled up and down during the period but closed where it began, so neither buyers nor sellers won.
Doji are read as indecision and potential turning points, especially after an extended move into support or resistance, where a stalling close hints the prevailing pressure is exhausting. Variants are named by wick shape — a long-legged doji has tall wicks both ways, a dragonfly doji has a long lower wick, a gravestone doji a long upper wick — each suggesting where price was rejected.
A doji on its own is a description, not a signal. It is one neutral candle, common in quiet markets, and only becomes a trade idea when paired with location and confirmation. Defining “open and close are equal” precisely (an exact tick, or within a small tolerance) is what makes it testable.