Histograms display the distribution of numerical data using intervals. The vertical axis is labeled with either number counts or percents. So, the height of the bar indicates the frequency of data values within an interval. Students can use histograms to group data into intervals. This allows them to see patterns in the data distribution and identify the overall shape of a distribution.
Because data are organized by intervals, the bars touch. This shows the continuous nature of the number line. There are conventions that determine where entries whose data values occur at the end points of an interval will be placed. This video shows how to construct a histogram, paying particular attention to where points on the borders of intervals belong.