Knowing is consumption. Like collecting ideas written on pretty stones; you hide them away in their little box, arrange them nicely, look at them in awe. But that's the extent of it; a pretty thing to dust never to be seen again, or worse: to be pulled out and treasure.
Understanding is akin to digestion. Things you understand are deeply ingrained with you all the time, shaping your actions, connected with everything else that's been digested.
Understanding the difference is extremely important.