How do you send a return shipping label?

[minimikimusic]

When a buyer opens a dispute for item not as described you are required to contact the buyer to send them a return shipping label. What does this actually mean? How do you send them a return shipping label? I post things using ebay satchels - am I supposed to mail them a satchel and shipping label for them to send the item back to me? What happens if the buyer doesn't reply to your message? 

Thanks,