Understanding a Mysterious Bitcoin Transaction I recently sent someone .5 Bitcoins, from the wallet on my Trezor.  

My Trezor wallet shows a transaction of -.5 bitcoins (actually slightly more than .5 because of the transaction fee of course).  Moreover, the balance showing on my Trezor is exactly what it should be --- that is, .5 less than it was before. And moreover, the recipient received exactly .5 bitcoins.  So it looks like everything went exactly as it should.

However, when I look up the transaction on the blockchain, I see this:



This appears to show 43.99 Bitcoins leaving my wallet, .5 of them going to the recipient, and the remaining 43.49 going to some mysterious other address.  

This almost makes it appear that somebody somehow managed to steal 43.49 of my Bitcoins, but given what's showing on the Trezor I'm not too worried about that. (As I said, the Trezor balance has been decremented by just .5, as it should be.  In case it's relevant, the total balance on the Trezor is substantially more than 43.99.)  

I'm guessing that somehow what happened is that for some reason the 43.49 extra Bitcoins were taken from my wallet and returned to me, but then I wonder why that doesn't show up on the list of transactions on my Trezor.  And the address to which the 43.49 were apparently sent does not match any public key that I have any record of ever having used.

Bottom line:  I'm not too concerned, but I'd sure like to understand this.  Can someone help?
if you have 50 BTC in one address and you are about sending 10 BTC to another address, Programmatically left bitcoins(40 BTC) in this address are the transaction fee. so some wallets sent remaining bitcoins minus the fee to a new address for privacy purposes. 

Almost all wallets don't show this transaction because its a transaction that you didn't make and it contains bitcoin change.