What is the true heart?

the "original heart" of Buddhism is also called sincerity and wholehearted. In Buddhism, there are many names: truth, self-nature, dharma body, reality, Buddha nature, dharma nature, Tathagata hiding, fulfillment, true colors, local scenery, great circle mirror wisdom and so on. The true meaning of one heart is incredible, that is, Zen Buddhism's "moving your mind is good, your mind is destroyed", and that is, Zen Buddhism's "opening your mouth is wrong and your words are broken". Here, I have to quote master lianchi as a far-fetched metaphor: "The heart is intangible, so there is nothing to be used as a metaphor. Generally speaking, the metaphor of the heart is a last resort. Let's describe it as if it is similar to the function of the heart, so that people can understand the concept of the heart somewhat, but we can't think that the heart is really like something. Give an example, for example, comparing the heart with a mirror. As we all know, a mirror can reflect things. When things are not facing the mirror, the mirror will not take the image of things into the mirror. When things are facing the mirror, the mirror will not hate them because of their likes and dislikes, beauty and ugliness; When the object leaves the mirror, the mirror will not keep the image of the object in the mirror. The sage's heart is always silent and always shines, and silence is spotless, and the photos are everywhere. This heart does not live inside, outside, or in the middle. San Ji is empty, but it is all-encompassing, and nothing does not shine. Therefore, using a mirror to compare the heart is just taking some of its similarities. After all, the mirror is an unconscious object. Is the mind as ignorant as the mirror? Moreover, the mirror loses its function in the dark, so how can it be compared with the wonderful and true body that is always silent and often shines? By analogy, the truth is the same, whether it is a metaphor for the heart with a orb or a metaphor for the heart with emptiness.