Bar charts, are one of the most basic charts around -- and have been since the Scottish engineer and political economist William Playfair, the founder of graphical methods of statistics, invented them in 1786. Playfair was a pioneer in the use of graphical displays, and the bar chart made its appearance in The Commercial and Political Atlas.
A bar chart has rectangular bars of the same height with widths that are proportional to the values they represent, with each bar representing a particular category. Their x-axis is quantitative, while their y-axis is categorical. Column charts are the reverse; the width of the rectangles is the same, while the height changes. Their x-axis is categorical, while their y-axis is quantitative. Essentially, in a bar chart, the bars are horizontally oriented, while in a column chart the bars are vertically oriented.
Bar and column charts are most often used to make comparisons between items. The length of each bar is proportional to a specific category.
Use bar charts to compare between different groups or to track changes over time. Keep in mind, though, that bar charts work best when the changes are larger and easier to see.