Acharya Prashant explains the critical difference between knowledge and understanding. He begins by stating that the saying about swallowing a fly one has seen is merely a saying, because one who has truly understood will never swallow the fly, no matter what. Similarly, one who has understood the nature of external influences will not be affected by them. The speaker clarifies that what people often mistake for understanding is merely an illusion; it is not understanding but rather having read or memorized definitions. You have not understood, you have only read. Understanding, he elaborates, means that life itself is transformed. Understanding is never confined to one specific area; one doesn't just understand a particular point, but life itself is understood. Everything is interconnected. When one veil is lifted, a hundred veils are lifted. It's like pressing one button that lights up a hundred bulbs simultaneously. Therefore, one cannot claim to understand one thing but not another, as everything is part of a complete circuit. The speaker contrasts this with gaining knowledge about a fly—its anatomy, the bacteria it carries. This is just information. This knowledge might create the illusion of understanding, but when one is intoxicated, they might still swallow the fly. This shows that the knowledge was not true understanding. You have not understood the matter; you have only gained knowledge about the fly and bacteria. Knowledge is something you acquire, while you, the acquirer, remain unchanged. It can be used by the ego for its own purposes, like a violent person gaining knowledge about weapons to further their violence. Knowledge is a tool in the hands of the ego. In contrast, understanding is not something you can collect; it fundamentally changes your very being. For understanding to arise, you must be willing to change. The speaker explains that one should ask themselves if their fundamental mental structure has changed after gaining what they call 'understanding'. If one is determined to hold on to their ego, their principles, and their deep-seated habits, they cannot become wise. Understanding is not a cheap thing that can be acquired by listening to a few words. If understanding were so cheap, one would surely swallow the fly. The sign of true understanding is when something within you breaks, when you feel the ground beneath your feet shifting. It involves both fear and attraction, a sense of death and rebirth. When you experience this, you can be sure that you are truly beginning to understand.