When the data that we want to visualize is in the form of a Polar Coordinate System rather than the Cartesian System, we call it Radial Bar Chart. They are in the form of circular bars one upon the other. The length of the bar represents the value of that category.
Why do you need it?
Radial charts are helpful basically to compare different categories using circular shapes. However, it is kept in mind that the outer bar is longer than the last one. The angle and radii of the bar play an important role here. Since each bar should be at different radii, hence there is a different angle for each bar.
What kind of data you can visualize with it?
Assume you want to show the percentage of people who use the internet in different countries, you can easily represent it using a radial chart effectively by using multiple circular bars that represent the percentage. As said earlier, radial charts are most effective in comparing two or more categories.