How is a Histogram constructed and how does it differ from a frequency polygon?

While constructing histogram the size of the item and their frequencies are represented in the form of rectangles. Each class is represented by a distance on the scale on X-axis and then respective frequencies are drawn on Y-axis. The heights of the bar is a measure of concentration of frequency. Histogram presents a frequency distribution arranged in class interval while frequency polygon is a graphical representation of a line joining the mid-values of the top of the frequency rectangles of histogram.