Gap

Trading is continuous only while a market is open. Orders and news accumulate while it is shut, over a weekend, a holiday, or the hours between one cash session and the next, and the opening auction or the first quote resolves them at whatever price clears. The distance from the previous close to that first print is the gap, and a chart shows it as a space no candle covers, because there is no price data to draw there.

Chart readers name gaps by where they fall: a common gap inside an established range, a breakaway gap as price leaves a range, a runaway or measuring gap inside a move already under way, and an exhaustion gap near its end. The labels are applied after the fact and analysts disagree about how far they can be told apart at the time, since the same gap is routinely reclassified as later bars print.

A widely repeated convention holds that gaps are eventually filled, meaning price trades back through the skipped range. Studies of it come out differently depending on the market, the period tested and the definition of a fill, and the convention carries no timeframe at all, so it describes a tendency rather than a rule.

Two things trip readers up. A gap is not the same as a fast move in a thin market, where trades do print but sparsely, and it is not the same as a chart drawn from bid or ask quotes showing a jump the traded price never made. More consequentially, no order can be filled inside a range that never traded: an order resting there executes at the next available price instead, which is the condition described under gapping.