Bar Charts are good for showing the changes over a period of time or for comparing data values of some objects. Its coordinate system is a bit different from standard cartesian system we are used to: the X axis that represent categories is vertical and the Y axis that is responsible for values is horizontal.
This Bar Chart shows the revenue in dollars of some company, only 10 most popular products are shown. The products’ names are used as labels of the X axis and of the bars. In the bottom of the chart you can see the Y axis representing the revenue made by selling this or that product.