Why, when you send Bitcoin, does a blockchain explorer show some of the coins coming back to another address of yours?
The UTXO and account models are worth understanding.
The account model is more like a regular bank account: the balance is easy to see, and writing smart contracts is more intuitive. The trade-off is that transactions from the same account must be processed in nonce order.
Don’t trade with borrowed money; the stress can push you into making bad decisions.
$BTC uses the UTXO model, so the balance shown in your wallet is actually the sum of multiple unspent outputs.