What are the difference between bar charts and histograms?

Question

are they applied to different kinds of variable, i.g. continuous or discrete data? thanks for answering.

Answer 1

A histogram is simply a specialized type of a bar chart in which the frequency of an occurence is placed on the x axis and the count of that frequency is placed on the y.  Similarly:

"The histogram differs from a bar chart in that it is the area of the bar that denotes the value, not the height, a crucial distinction when the categories are not of uniform width (Lancaster, 1974). " (wikipedia)