The valley spirit never dies, this is called the Mysterious Female. The gate to the Mysterious Female, is the root of Heaven and Earth. Continuous as if it existed, it is used effortlessly.
This is a direct quote from the Tao Te Ching.
Simply put, it means the eternal Dao between Heaven and Earth breeds everything, endlessly.
Wang Yunxiao's educational level isn't high, so he can't understand the allusion here, but can only let Old Third Ding explain it in detail for him.
According to the theories of Taoism, the "Dao" is the mother of all things and is feminine; this is a descriptive portrayal.
But as everyone knows, average people can't elevate their thinking to such a high level.
They could only understand things within their knowledge scope; exceeding that results in self-delusion and transformation.
