Histogram

Histograms are similar to bar charts but with one crucial difference. The bars in a bar chart show their value by the height, whereas, in a Histogram the width of the bars relates to its value and the height refers to the frequency of the value. In a bar chart each bar represents a different category while its height represents the frequency the category comes up. In a Histogram each bar represents the same category but indicates the value or range of values by its placement along the horizontal axis and its occurrences by its height relative to the vertical axis. Easy way to depict the two graphs is that a bar chart’s bars will have space between them and a Histogram’s bars usually don’t.

The graph shown is a Histogram of “Distribution of salaries of the Acme Corporation.” The Horizontal axis displays the salary ranges of the employees in thousands. The vertical axis displays the number of employees that earn a salary in the salary ranges.

http://www.statcan.gc.ca/edu/power-pouvoir/ch9/histo/5214822-eng.htm