圈 (juān) means 'to confine, pen in' — it specifically suggests enclosing someone or something in a limited space, often with a physical barrier like a room or cage. It's more vivid and concrete than 限制 (restrict/limit), which is abstract; and unlike 关 (guān, to shut/confine) or 锁 (suǒ, to lock), 圈 emphasizes the act of surrounding or corralling.