As you can see, the bar chart can visualize percentages. When you have categories that you want to compare based on numerical values, you can use a bar chart. This includes frequencies (if you're visualizing the distribution of a categorical variable), percentages (if you're comparing parts of a whole), or any other numeric value. Its simplicity and effectiveness make it a very universal chart.
We've just used a bar chart to visualize parts of a whole. In the exercise on the right, you can assess how this approach to the 'part of a whole' problem differs from that of a pie chart.