A bar chart or graph is a simple visual tool commonly used to show the relative frequencies or counts of the levels of a categorical variable. It shows rectangular bars arranged vertically (along the X-axis) or horizontally (along the Y-axis) with the frequencies shown on the other axis. The bars respresent the categories or levels and the heights of the bars represent the counts for those categories.
The bar chart allows one to compare the relative representation of the different levels of the variable within the sample. The bars on the chart are separated by spaces in between them, to indicate the discreteness of the levels.
The bart charts shown are of the number of fruit in a box classified by type of fruit (apples, oranges, bananas).
Bar charts can also be used to show the sample statistics (mean, variance, etc.) or other characteristics of the categories. More complex bar charts can be obtained to compare the different levels across two or more groups, or to show multiple characteristics in a single graph. The Pareto Chart is a type of bar chart.