What Is a Block?
Blocks within a blockchain are arranged sequentially, with new blocks added at the end of the chain.
In addition to a timestamp and a record of transactions, each block also includes the solution to a unique cryptographic puzzle.
This puzzle must be solved through mining for a new block to be added to the blockchain.
Miners who successfully solve the puzzle are rewarded, and thus, the details of the rewarded addresses are included as the first transaction in each block.
Genesis Block and Blockchain Security
The first block in a blockchain is known as the genesis block, and it does not reference any previous block since it is the starting point of the chain.
The block structure of a blockchain ensures its high level of security and integrity.
Each block in the chain contains a hashed reference to all the preceding data, making it extremely challenging to alter any record within the blockchain.
To modify a single record, a malicious actor must change every block in the chain, which is practically impossible.