Although there is an idiom in this text, tell me what it is.

"Book of Rites": "Although there is delicious food, I don't know its use. Although there is supreme Tao, learning, I don't know its goodness. It is to learn and then know the deficiency, and to teach and then know the difficulty. If you don't know enough, then you can reverse; Advance despite difficulties, and then strive for self-improvement. So teaching and learning are also beneficial.

The idiom here is "Ji à Ji à o Xu é xi ā ng zh m ng", which means that teaching and learning interact and promote each other, and both of them can improve their academic qualifications and increase their knowledge. L: promotion.

One of the goals pursued by teachers is to learn from each other.