How does change address interact with original address change address is an additional address inside a wallet, which u can create with a raw transaction with 2 outputs.
What I want to know is how does this change address interact with the (for a lack of words) &quot;original&quot; address, when sending money back to the &quot;original&quot; address.
Does the change address have a pre-written script which sends BTC back to &quot;original&quot; address?
There is no relation at all between the two addresses, except that they're owned by the same person/wallet.
At the protocol level, &quot;change&quot; does not exist. It's just another output (with a corresponding address), indistinguishable from normal &quot;payment&quot; outputs. It is your wallet that's creating it: it needs a place to send the remainder of a spent UTXO of yours that you don't actually want to transfer, so it creates a new address of its own (just like you'd do when receiving funds), and sends the remainder there. And it stays there, until there is a need to spend those funds. It could send them back to the same address, but this would be a serious privacy leak (it lets people distinguish change from payment), and have no cost advantage.