Visualization of Open, High, Low, Close (OHLC) within a specific time frame.
Example
After a sell-off, a candle forms with a small body and a long lower wick — a 'hammer'. The long wick shows sellers pushed price down, but buyers reclaimed it by the close. At a support level that is a possible reversal signal. But single candles are never a complete signal — they only gain meaning in the context of trend, volume and key zones.