A radar chart is a graphical method of displaying data that really only shows that the person who made the chart is a pretentious asshole.
Tom is presenting his data using a confusing radar chart, even though a pie chart would be less confusing and works just as well.
A radar (or spider) chart is a chart that looks like shit. All the lines overlap and it's impossible to read. The only useful information ever provided by a radar chart is whether or not the person who made the chart is an asshole.
I spent 10 minutes looking at this radar chart, and by the time I gained a glimmer of useful information from it, I had a headache.