piggybackare separate concerns.
TX1where Alice sends 0.5 ETH to Bob using an input
UTXO1worth 1 ETH. The transaction will have two outputs:
UTXO2owned by Bob (0.5 ETH)
UTXO3owned by Alice (0.5 ETH)
TX1but both Alice and Bob must piggyback with a reference to their respective outputs in order to exit their funds.