This is a diagram of which shapes fall into which categories based on the properties of that shape. For example, a square is a special kind of 2-D, quadrilateral, trapezoid, parallelogram, rectangle and rhombus, so it is at the end of that trail of categories.
The chart is meant to eliminate confusion about which shapes fall into which categories. I found a lot of students had a hard time grasping "wait, a rectangle is a type of parallelogram? and a square is a type of rectangle?", so I felt t