Five-number summary

The five-number summary captures the center and spread of a distribution with five ordered values: minimum, $Q_1$ (the first quartile), median, $Q_3$ (the third quartile), and maximum. For example, the summary 2, 5, 8, 12, 20 says the data run from 2 to 20 with a median of 8. These five numbers are exactly what a boxplot draws, and the gap $Q_3 - Q_1$ gives the interquartile range. Together they describe spread without assuming any particular distribution shape.