UTXO (Unspent Transaction Output) is the output of previous transactions that havent been used as input for new transactions in blockchains like Bitcoin.

UTXO (Unspent Transaction Output) is a fundamental concept in the accounting model used by blockchains like Bitcoin. In the UTXO model, each transaction has one or more inputs and outputs. The inputs are Unspent Transaction Outputs from previous transactions, while the outputs are new Unspent Transaction Outputs that can be used as inputs for future transactions.

When someone sends Bitcoin, they are not actually sending the coins themselves, but rather spending the UTXO from the previous transaction they had and creating a new UTXO as an output. This output can then be used as input for new transactions in the future.

Each UTXO has a specific denomination value in Bitcoin units and can only be fully spent in a new transaction. If you want to send an amount smaller than the UTXO value, the transaction will generate two outputs: one for the amount you want to send, and one for the change you have.

The UTXO model ensures that every transaction on the blockchain is valid and no double-spending occurs.