1. Yes, a refund indicates a seller giving some or all money back to the buyer. If you're trying to ask a more specific question than that, I don't understand it, please rephrase/elaborate.
2. You set your own return policies on eBay. you can accept returns (in which case you accept returns for ANY reason, including the buyer doesn't want it anymore) or you can state no returns. If you state no returns and the buyer claims the item is not as described, you will be accepting a return or you will be refunding the buyer without a return, however.
3. If a buyer intentionally (or accidentally) damages an item and returns it to you, you can report the buyer for abusing return privileges. Depending on the buyer's previous record and your own record on eBay, plus any facts that can be provided (emails back and forth, whatever) eBay will decide who to side with.
4. If a buyer claims non-receipt on a shipment under $250 and the seller has tracking that shows otherwise, the buyer will lose. Over $250, the seller must also have a delivery signature.
You can read up on a lot of this on the eBay seller help pages. They are extremely beneficial to new sellers, and even old biddies like me occasionally find something we didn't know (or that has been changed) so they're worth making a regular part of your work routine.
Edited to add: Since you're in Australia you may want to ask these questions on the Australian sellers forum on eBay. Not all eBay rules are worldwide - there are some differences between ebay.com and ebay.au, etc.