A gap is an area on a price chart in which there were no trades. It is easy to see gaps if you take candle stick charts. Let us try to understand gaps in another way. The fluctuations in stock prices are coherent in nature. That means that the price rises or falls gradually. Thus, in rising scrip, if on one day the low was Rs 100 and the high was Rs 135, on the next day the low would be Rs 130 and the high Rs 140. Here, the low for the next day falls within the high-low range of the previous day. But suppose for the second day, the low was Rs 145 and the high Rs 150. Then, the low for the next day has fallen above the previous day High-Low range, or it was higher than the previous day’s high. So, when one draws bar charts showing High-Lows every day, there would be a discontinuity, termed as a ‘Gap’ in technical theory. An interesting feature of Price gaps is that it gets filled within a short amount of time. That is, the price would come back to fill the price gap of Rs 140 – Rs145, where there was no trade in the previous days.
In simple terms-a gap occurs when the current bar opens above the high or below the low of the previous bar. On a price chart, a space appears between the bars indicating the gap.