What Is the Purpose of a “Block Header” in a Blockchain?

The block header is a small section of data that summarizes the contents of the entire block and is essential for the Proof-of-Work mechanism. It contains key metadata, including the hash of the previous block, the Merkle Root of all transactions, the timestamp, the difficulty target, and the nonce.

The header is the only part of the block that is hashed repeatedly by miners to find a valid solution, securing the chain and validating the transactions.