GAP is the difference in the trading range, which can be seen using candlesticks charts. The chart will indicate a GAP in the candlestick view. GAP indicates the strength of the trend and helps to locate whether the trend is at early stage, breakout stage or at terminating stage.
In a technical analysis chart, a gap represents an area where no trading takes place. It is is essentially an empty space between one trading period and the previous trading period.
The GAP is formed when there is a large-enough difference in the opening price of a trading period where that price and the subsequent price moves do not fall within the range of the previous trading period.