What is understanding? It's not merely knowledge or comprehension. "In a phrase, understanding is the ability to think and act with what one knows," wrote education expert David Perkins, PhD, in the book Teaching for Understanding: Linking Research with Practice."In keeping with this, learning for understanding is like learning a flexible performance—more like learning to improvise jazz or hold a good conversation…than learning the multiplication table," Dr. Perkins wrote. "Learning facts can be a crucial backdrop to learning for understanding, but learning facts is not learning for understanding.