What is a Treemap Chart?
Treemapping is a data visualization technique that displays hierarchical data using rectangles of decreasing sizes, often called nesting, to create treemap charts. As the name suggests, treemap charts depict data in a tree-like format, with branches and sub-branches that are able to be read at a glance. Treemaps are great at taking a large amount of raw data and depicting it in a visually appealing, compact, and easy-to-read manner, enabling the user to discern patterns and make comparisons rapidly.
Source:
https://www.tibco.com/reference-center/what-is-a-treemap-chart