This site showed a mind map of the Van Hiele Model of Geometric thought. It incorporated the levels as well as properties and phases of learning that students should progress through. Most sites focused just on the levels – I liked that this presented the levels and more, and in a visual representation. Specifically, the phases of learning provided specific tips for math teachers in the classroom.
I think the model applies to individuals and the levels each of them must go through in order to fully understand geometry. It correlates, to me, to differentiated learning. Lesson plans must take into account that not everyone will be at the same level in the classroom. An ideal lesson plan will have components for each level.
I believe a person can be at different levels, depending upon their learning style, ability, and the content. For example, someone could be at level two with rectangles but may not fully be at level two for hexagons or triangles.