Why does it say a total of 0.09 BTC was sent when I only sent out $ 100?
You can think of the block chain as being a storage for safe deposit boxes, which we call “outputs”. These outputs are just containers that hold amounts of bitcoins. If someone sends you 0.1 BTC, he'll fund your address with an output holding 0.1 BTC, that can only be unlocked by you. If you then want to spend 0.2 BTC, you'll have to unlock that output create a new one that spends 0.2 BTC to the receiving address and 0.8 BTC to you as change.
(excluding the mining fee)That other address your Ledger chose to sent the remaining bitcoins is called a “change address”.
— But, BlackHatCoiner, why didn't it choose to send the change to my sending address instead?Because of your privacy. The block chain is publicly known and can be accessed by anyone, anytime, maybe 'til the next century. If someone sees that
Address_A sends 0.02 BTC to
Address_B and the remaining to itself, it'll mean that the owners of that address haven't spent their coins yet. But, if he sees that
Address_A sends 0.02 BTC to
Address_B and the remaining to
Address_C there's no actual way to know if you still have money.