A bar graph is used to compare items between different groups and track changes over a period of time. Bar graphs are best used for changes that happen over a large amount of time instead of just months or weeks.
Bar graphs feature rectangular bars with lengths that are directly proportional to the values they represent. A bar graph can be plotted both vertically, which is sometimes referred to as a column bar graph, or horizontally. Bar charts also resemble histograms, which can display a record of continuous data, but the main difference is the type of data that is represented in the two.