On-yomi 「音読み」 is the term for the Chinese reading of a character in Japanese, such that it inherited its pronunciation from the original Chinese.
「葉」 This character represents the concept of a leaf, a blade, a needle, or similar things.
It's on-yomi, or Chinese, reading is "you"「ヨウ」, while it's
kun-yomi reading is "ha" 「は」, and it's
nanori is either "yo" 「よ」 or "wa" 「わ」.