Block

Definition

A block is a structured collection of transaction data that a blockchain records as one step in its history. A Bitcoin block contains a header and a list of transactions, beginning with a special coinbase transaction. The header links to a previous block and commits to the included transactions through a Merkle root. Miners search for a header hash that satisfies the proof-of-work target, but finding such a hash is only one requirement for acceptance. Full nodes also check transaction validity and other consensus limits. A block can be valid without remaining in the eventual best chain if competing branches are discovered. The term therefore describes a data structure, not an unconditional promise of final settlement. Block explorers display its hash, height, timestamp, transaction count, and other details, each of which answers a different question about the recorded history.