The change mechanism is designed to deduct all the assets of the whole transaction when sending the transaction, with the remaining assets except the transacted amount to be returned to the wallet. The returned part is known as change given. For example, I have 10 BTC in the wallet transferred in as one sum. Now I need to transfer out 8 BTC and 0.1 BTC, so I have to pay all the 10 BTC, and 1.9 BTC will be returned. And the 1.9 BTC is known as the change.
