In reply to Dr D E Gray.

Thank you for your opinion. The vertical axis of a histogram is proportional to the frequency. You can choose to scale the axis so that it represents a frequency (count), a percentage (value in [0,100]), a proportion (value in [0,1]), or a density. All are valid, and each is useful for various purposes.

The main difference between a bar chart and a histogram is that the bar chart represents counts (or percents, or proportions, or densities) of a discrete variable whereas a histogram represents binning a continuous variable. Because the first figure is formed by binning a continuous variable and counting the frequencies in each min, it is a histogram.