Practical understanding of let’s say Newton’s Physics is of the type which is offered by the text books. Students understand the statements of laws along with mathematical depiction thereof and become able to solve numerical or exercise questions. After completing the study in this way, they may become good engineers or professors of physics.
But those who become scientists, they seek understanding of a different kind that may be regarded as intellectual understanding. They not only pursue to understand book contents within the context of daily real life observations, more importantly they also try to investigate the history and logic behind theories of science that they read in text books. Rather than trying to solve text books exercise questions, their efforts are usually focused at finding how the theory in question was actually derived or discovered by the original scientist. The practical understanding makes one able to apply theory in practice whereas the intellectual understanding would make one able to not only improve or refine the existing theories but to propose or formulate new theories as well.