In computing and information visualization, treemaps are a way of displaying hierarchical data with nested rectangles. Each branch of the tree is given a rectangle, which is then tiled with smaller rectangles representing sub-branches.
Data in a treemap is displayed in "branches" (also called "nodes"). Each branch can have zero or more sub-branches, and one parent branch (except for the root, which has no parents). Each branch is displayed as a rectangle, sized and coloured according to the values in your data. Sizes and colours are valued relative to all other branches in the graph.
Imagine that our data is such in this table:
This might look boring. Also and most importantly, it is not easy to grasp the general idea of values. With a treemap, we can show it like this;
So we can see how much pretty birdseed we have on the shelf compared to parrot perch and so others.