Learn in the textbookBasic Charts and Visualizing Distributions
DefinitionA box plot (箱ひげ図) uses the values that split data sorted from smallest to largest into four parts of equal count (the quartiles, 四分位数), together with the minimum and maximum, to summarize how the data spread as a box with whiskers.
ExplanationCounting from the small end, the quartiles are the first quartile, the median (second quartile), and the third quartile. The box spans from the first to the third quartile and holds roughly the middle half of the data, and whiskers extend from both ends of the box to the minimum and the maximum.
AnalogyDescribing a marathon's finish times by the leader, the main pack in the middle and the last runner conveys in a few words how spread out the whole field was.
Memory hookA cat's face seen from the front: the box is the face, and the lines reaching left and right are its whiskers.