A histogram represents the distribution of numerical data. To create a histogram, the frequency of data within a range of values will need to be bucketed into intervals. Opposed to bar charts, histograms display the frequency of continuous data. The red line displays the normal distribution. The Mean - stdDev (stdDev – standard deviation), Mean and Mean + stdDev lines display statistical means. The Minimum line displays the minimum count.
See Histogram for more information.