Box Charts are usually used when we need to show not only the mean or median values but the maximum and minimum with a median and quartiles, which make the story more complete. This chart type is popular in finance and economics for showing statistics. Box Charts use basic Cartesian coordinates. There can be several series on a plot, and then you can compare both distributions; boxes can be put either horizontally or vertically. Differences between the parts of a box allow defining degree of dispersion and data asymmetry and identifying outliers.
This is a simple Box chart, where we can see the statistics for delays of Oceanic Airlines flights in December of 2014. All these boxes are points of one series; each box represents delays in a region specified below, on the horizontal axis, as categories are regions. Each box hold the information about minimum and maximum delays’ durations, the median value and the quartiles: the line inside the box is a median (also known as second quartile. Note that median is not a mean value!), bottom and top of the box mean the first and the third quartile, and the points where the whiskers end are the max and the min values. The duration values in minutes are spread along the vertical axis.