Tell me what it is.

Chen Yaozi was good at archery. At that time, no one in the world could compare with him, and he was proud of it. Once, he shot an arrow in his garden. An old man selling oil put down the burden he was carrying, stood aside and looked at him casually, never leaving. The old man saw that Chen Yaozi could shoot eight or nine of the ten arrows, but he nodded slightly in agreement.

Kang Su Gong asked, "Can you shoot arrows, too? Isn't my archery also superb? " The old man said, "There is no other mystery, but familiarity." Kang Sugong said angrily, "How dare you despise my archery!" The old man said, "I can understand this truth from my experience in pouring oil." So the old man put a gourd on the ground, covered its mouth with copper coins, and slowly poured oil into the gourd with a spoon. Oil was injected from the hole of the copper coin, but the copper coin was not wet. The old man said, "I have no other secrets about this skill, but I am familiar with it." Seeing this, Chen Yaozi had to send the old man away with a smile.

The truth of the story:

The story of "Oil Man" reveals the truth that "practice makes perfect".