A range bar completes once the distance from its high to its low reaches the chosen range. A 10-tick range bar on a futures contract closes as soon as the bar spans 10 ticks, then a new bar starts.
In fast markets you get many bars per minute; in quiet markets a single bar can last an hour. That makes volatility visible as bar frequency rather than bar size, and it keeps indicator inputs on a constant scale.
The trade-offs: gaps can produce bars larger than the setting, backtests on range bars are easy to get wrong because the bar boundaries depend on the data feed's tick granularity, and comparing results across brokers can be impossible. Range bars change the look of a chart far more than they change the underlying edge.
Related: tick-chart, renko-chart, volume-bars, timeframe