The coinbase transaction’s value is based on factors such as each individual transaction’s value, block height, and halving. Miners can add any customizable text to the blocks they have created.
The value of a coinbase transaction is determined by several factors. These include the value of every transaction validated by the block, the height of the block (number of transactions) and the halving relative to the block. Once the block has reached 100 confirmations, the miner can use the BTC.
When a block is created, it holds approximately 100 bytes of data. There is also an allocation for miners to include any text they prefer. Nakamoto, for instance, wrote the following message when they mined Bitcoin’s genesis block:
This message is a reference to a headline in the British newspaper The Times from Jan. 3, 2009, and is often seen as a commentary on the state of the global financial system at the time of Bitcoin’s creation.
Nakamoto chose to embed this message in the genesis block to emphasize the need for a decentralized and trustless system of transactions, free from the influence of central authorities and intermediaries.
Moreover, miners can add any information they choose to personalize the block, sending an unalterable message in perpetuity.
Source: https://cointelegraph.com/explained/what-is-a-coinbase-transaction
