Bitcoin transactionA transfer of Bitcoins from one party to another. The Bitcoin transaction is created in the digital wallet and transmitted to the Bitcoin network where it is validated by a Bitcoin "miner." After successful approval, the transaction is entered into the blockchain ledger. See Bitcoin mining.
UXTOs and Inputs
Because a person's Bitcoin holdings may span numerous blocks in the blockchain, the Bitcoin wallet scans the blockchain looking for every "unspent transaction output" (UXTO) that contributes to the user's Bitcoin balance. Either the wallet itself or a third-party service maintains a database of UXTOs for the Bitcoin holder. Each UXTO is indivisible and cannot be divided. Therefore, if the UXTO is larger than the amount to be paid, change is made in the form of a new UXTO back to the user, the same as making a cash payment of $6 with a $10 bill and receiving $4 in change.
To make a payment, the wallet creates one transaction input that points to a UXTO and unlocks it with a digital signature that proves ownership. The transaction is broadcast, and every node that attempts to validate it retrieves the UXTO. See SegWit, Bitcoin wallet, Bitcoin mining, Bitcoin and blockchain.