Explain the Difference Between Knowing and Understanding

You can know a large number of facts about something and still be unable to use them in a new situation, apply them to a problem, or explain them to someone who does not already know them. That is the gap between familiarity and understanding. This makes the distinction tangible and gives you a practical test for the topic you chose.

I want to understand the difference between knowing a fact and actually understanding it, because I think I have been confusing the two in my learning.

A topic I think I know but might only be familiar with: [describe a subject area where you have a lot of information but sometimes cannot use it well]

Explain to me: what the difference between knowledge and understanding actually is (not just as a definition but as something I can feel the difference between), how to tell which one I have on a given topic, and what kind of practice or task crosses the line from memorisation into genuine understanding. Give me a specific test I can apply to the topic I described to find out which side I am on.