Radial columns are columns represented in a radar or polar circular area. Take a regular single-series column chart and bend it into a circular area to get this chart type.
Our US Sales single-series demo charts show product quantities sold every year between 2000 and 2017 in US. Histograms use the same data. And you can take the columns displayed by those histograms and bend them into the circular polar areas of these new charts, for a different representation.