used to express surprise or confusion, to ask someone to repeat what they have said, or as a way of getting someone to give some type of reaction to a statement that you have made

"Janet's leaving her husband." "Eh?" “珍妮特要离开她丈夫了。”“什么?”

"Did you hear what I said?" "Eh? Say it again - I wasn't listening." “你听见我说什么了吗？”“啊，你再说一遍——我刚才没有听。”

Going overseas again, eh? It's a nice life for some! 又要出国，啊？有些人的日子过得真不錯！