Unspent Transaction Output or UTXO is defined as cryptocurrency received by your wallet that is available for you to spend.
Bitcoin and other cryptocurrencies based on Bitcoin’s technology need a way to keep track of every single bit of money. They then categorize it as either unspent (available) or spent (unavailable).
If you were to total up the UTXO, you would get the user’s available balance. In other words, the UTXO is how much Bitcoin he actually has.