I couldn’t find a wikipedia based definition, but the best synopsis I saw was (ironically) a Microsoft Power BI resource, which defined them as “squarified pie charts”. A perk of this method of representing data is that it doesn’t require the user to try to interpret angles.
Andy Kriebel uploaded this video in January 2017:
Russell Christopher inspired Andy’s blog post and video with this article:
Whilst Andy’s blog post can be found here:
Rajeev Pandey was inspired to write up the process of creating these charts, following Andy’s video:
Andy’s example workbook is here.