In Bitcoin Qt, what does "Message" mean in the request payment form? In Bitcoin Qt, if I go to "Receive" and right click on an address, one of the options is to "Show QR Code" for an address. Below the QR code, there is a form looks like this:

[ ] Request payment
Amount: ____ BTC
Label: ____
Message: ____


My question is: what does the "Message" field do?
The Bitcoin protocol does not support any kind of message associated with transactions. The message when generating QR codes is simply a short string that is passed along with the Address and Amount to the person scanning the QR code as a hint to recognize what the Address has been used for. A merchant may for example put a short description of the item you bought in the message field. You then scan it and your Bitcoin client may use that field to mark the transaction, so that you later recognize which transaction was used for what.

The message however will never be posted to the network and is only stored in your Bitcoin client, i.e., if you restore your wallet the messages may not be restored.