It's a metaphor.
I think modern Western society is so steeped in the left hemisphere that they, by and large, don't and can't understand metaphor, which is largely a function of the right hemisphere of the brain.
All understanding and explanation is only metaphor. Words and abstract concepts are a shaperned, abstracted, and many reflection removed medium of the same. (i.e., a sensation, a thought, a thought about a thought, and so on. All thoughts are about sensations or another thought. It all comes back to one ultimate metaphor, the first person perspective. The metaphor is what one of those is or can be like, as experienced and intimately known)
I think it's immensely helpful to understand metaphor to understand non-duality, and if you understand metaphor, I can simply say that the teaching is the empty metaphor. The metaphor with nothing in it. If you understand metaphor, there's literally nothing else to say, nothing else to understand. Understand the metaphor, drop the metaphor, instantiate the metaphor.