The Coinbase transaction was created by miners, mainly to reward miners for their efforts to carry out POW mining. The reward is divided into two parts. Part of it is a block reward, and this part is relatively fixed. At present, the block reward for each block is 12.5BTC, which is halved every four years. The other part is the handling fee. Each transaction of the current block will contain a certain reward for miners, that is, the transaction handling fee. When creating Coinbase transactions, the mining union accumulates the handling fees in all transactions and then transfers the money to itself. Coinbase transactions are characterized by no "parent transaction". Input is required in ordinary transactions, and input comes from the output of the parent transaction, so ordinary transactions have parent transactions. However, Coinbase transactions do not have parent transactions, because coins are generated directly by the system.