A box plot shows the median, the quartiles, and the spread. The box is the middle 50 percent. The line inside the box is the median, not the mean. Mean, median, and mode as numbers are in mean, median, and mode.
Read the five numbers
Left whisker is the minimum (or a low fence). Left edge of the box is Q1. Middle line is Q2, the median. Right edge is Q3. Right whisker is the maximum. A long whisker means a long tail, not a higher median. Standard deviation is a different spread measure, in standard deviation.
Scatterplots show two variables at once, not five-number summaries, in scatterplots and correlation. Charts on Math more broadly are in charts and tables.
The bottom line
Median is the line in the box. Spread is the width of the box and the whiskers. Do not confuse either with the mean.
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