A graphical display to summarize the distribution of a sample. It displays five numbers plus (possibly) some outliers - those five points being the median, hinges (approximate quartiles), and the largest and smallest value not counting any points marked as outliers.
A boxplot or box-and-whisker plot is a graphical display that summarizes a sample distribution. Mostly used when comparing many samples, it displays five numbers plus (possibly) some outliers. The five numbers are the median (drawn as a central line) and hinges - approximate quartiles - for which a box is drawn. Then lines are drawn out to the largest and smallest values not marked as outliers. There are many variants of the basic boxplot.