This tool detects outside bars (or candles) and their subsequent inside bar(s). An outside bar is a bar which (a) closes outside the high-low range of the previous bar and which (b) is followed by a bar which closes within the potential outside bar’s high-low range. German trader Michael Voigt uses outside and inside bars frequently, including for placing some of his stops.
In this example the outside bar is number 1. Number 1 is an outside bar because (a) it closes outside the high-low of range of the previous bar, and because (b) number 2 closes within the high-low range of number 1 (at the same time making bar 2 the first inside bar). In total there are 5 inside bars (numbers 2 to 6).