There are three kinds of understanding: intellectual understanding, experiential understanding and existential realization.
Intellectual understanding says “yes,” it agrees. Experiential understanding feels, is obvious. Existential realization is irrefutable. It becomes your very nature.
All you hear will simply remain a jumble of words if there is no experiential understanding, which is more on the feeling level. You can know intellectually that you are hollow and empty, but sitting and feeling that you are hollow and empty is totally different.
When one gets an experience, one wants to understand more about it and becomes a seeker. If you have only intellectual understanding, you will think you know it all. Most theologians are in this category. Existential realization contains within it both experiential and intellectual understanding. But it is beyond both of these.