I like to think of knowledge as a tree. A tree grows from a seed from which it sets small roots and eventually builds branches and leaves. If the roots are not strong enough, the leaves and branches weaken. You will find the same with all knowledge you gain. If your ground-knowledge (roots) is not good enough, you will have a hard time to understand the specifics (branches and leaves) about a topic. That’s why I will always check first whether you did understand the roots of the topic.