As mentioned previously, a block is a permanent store of the transaction recorded and validated during a given time period. Technically, the transaction data is written to a read-only file called a block. When we look into the details of a block, it represents the present and contains transactions that have been recorded recently, as well as a reference to the past. Each time a block is finalized, it becomes part of the past and cannot be altered or removed. The blockchain works in a cycle where new transactions are stored in the next block with a reference to the preceding block. The structure of a block depends on the blockchain.
The following table shows the structure of a block used in the bitcoin core code:
