Dregs: the residue left over from making wine. Essence: The best part of something. A metaphor for the crude and useless parts of things. Absorb the good things and discard the bad and useless things. It means to learn from each other's strengths. It is also used to remove the dross and retain the essence.
In "The Doctrine of Use" published by Lu Xun on June 7, 1934, he mentioned the meaning of "removing the dross and taking the essence", but did not use this term explicitly. Essence: the best part of something, dregs: things like distiller's grains and bean dregs, which metaphorically refers to useless things. Take the best from things and discard the bad and useless things from things.
For individuals, the attitude and method of accepting foreign or new cultures or things. Accept what is good and useful, discard what is useless and harmful, and digest what is suitable for you.
Extended information
The source of removing the dross and extracting the essence:
Manan Village's "The Secret of Not Wanting Secrets": "We now advocate the use of criticism in reading. The perspective is to select the essence and discard the dross. Ancient scholars did not have the courage to propose this idea. "
Synonyms:
Remove the rough and select the essence, and use macro to extract the essence."