A Zero Confirmation Transaction (ZCT) is a type of transaction in which a transaction is not confirmed until a block is mined. Once a block has been mined, a transaction is confirmed by the rest of the network. The time that it takes for a transaction to be confirmed depends on the number of transactions on the network.
Unlike a confirmed transaction, a Zero Confirmation Transaction is not displayed on the blockchain. This makes it fast and convenient for both merchants and customers. However, some people are against this type of transaction because it can lead to double-spending, which can be a serious issue. Some initiatives have been introduced to address this problem.