圈 (juān) means 'to confine, to pen in' — it specifically describes physically enclosing animals or people in a small space, like a pen or cage. Compared to 关 (guān), which is a general 'to shut in' (e.g., 关在房间里), 圈 emphasizes the idea of a tight, enclosed area; 限制 (xiànzhì) is broader 'to restrict' (rules, limits), not physical confinement.