Inputs, outputs, and change
A transaction spends existing unspent transaction outputs, called UTXOs, and creates new outputs. You can think of an input as using an entire payment you previously received. A wallet can create an output for the recipient and another for your change.
This is a mental model, not physical cash inside a wallet. The ledger records which outputs remain spendable.
The fee comes from the difference
For an ordinary transaction, the total input value minus the total output value is the fee. Fee rates are commonly expressed in satoshis per virtual byte. Transaction size and demand for block space affect fee selection; the fee is not simply a percentage of the amount sent.
More inputs can make a payment larger even if the amount is small.
Broadcast is not confirmation
Signing authorizes the transaction. Broadcasting sends it to peers. Nodes may keep an unconfirmed transaction in a local mempool; there is no single universal queue guaranteeing inclusion. A miner can include it in a valid block, giving it a first confirmation.
Later blocks increase its confirmation count. An unconfirmed payment and a confirmed payment carry different risks.
Check before you authorize
Review the destination, amount, units, network, and fee. If a signing device has its own trusted display, verify the details there. Copying an address or scanning a code does not remove the need to inspect the result.
A blockchain explorer can show transaction status, but it also learns what you search for. Neither an explorer nor a screenshot guarantees that a service has credited your account.
Try the idea: a payment with change
Suppose a wallet spends a 100,000-sat output. It creates a 30,000-sat payment and a 69,000-sat change output. The missing 1,000 sats are the fee: 100,000 minus 30,000 minus 69,000.
For a separate size example, 150 virtual bytes at 5 sats per virtual byte implies a 750-sat fee. These are learning numbers, not a current fee recommendation.
A common misconception: every transfer needs the same fee
Two payments sending the same amount can have different transaction sizes. One wallet might need to combine several small outputs; another might spend a single output. The selected fee rate also reflects the sender’s timing preference and conditions in the fee market.
Before you move on, calculate the fee from a sample transaction’s inputs and outputs. Then explain why an estimated waiting time is an estimate rather than a deadline or a promise that a particular miner will include your payment.