For each unit in the chosen medium context (NUTS 0 for example in Figure 9.4), this chart shows the dispersion of the medium deviation for the territorial units at sub-levels (NUTS 2 level in Figure 9.4).
A boxplot typically provides the following information:
two lines show the values between:
the minimum and first quarter Q1
the third quarter and maximum Q3
a box shows the interquartile Q1-Q3
a line shows the mediane value