1. Explain it simply
却 (què) means 'yet' or 'but', marking a contrast that runs against expectation.
Word order: first clause, then Subject + 却 + verb / adjective, as in 他很努力，成绩却不太好.
Unlike 但是 and 可是, 却 does NOT head the clause - it sits inside, right after the subject.
却 cannot move in front of the subject or fall to the end of the sentence.
2. Show examples
这件衣服很贵，质量却不好。
Zhè jiàn yīfu hěn guì, zhìliàng què bù hǎo.
This piece of clothing is expensive, yet the quality is poor.
却 sits after the subject 质量
大家都很着急，他却很冷静。
Dàjiā dōu hěn zháojí, tā què hěn lěngjìng.
Everyone was anxious, yet he stayed calm.
the contrast is unexpected
我给他打了电话，他却没有接。
Wǒ gěi tā dǎ le diànhuà, tā què méiyǒu jiē.
I called him, yet he didn't pick up.
却 comes after 他, not before it
3. Share a tip
Remember 却 goes AFTER the subject - say 他却很冷静, not 却他很冷静, the way 但是 would.