When switching between a chart and the reverse chart option, the difference is that the focus of your analysis is reversed. For example, if you have asked males and females if they prefer the color red or blue, your data will initially be displayed by sex i.e. male and female responses broken down by color preference. By switching to the reverse option of the chart type, you will see the results displayed by color, i.e. red and blue responses broken down by male and female.
This function is also very useful for displaying cross-tab analyses in chart form when you need to display more than one category.