On the bitcoin blockchain network, a block contains one megabyte's worth of bitcoin transactions. The bitcoin blockchain grows larger as more transactions are made, resulting in more blocks containing transaction data. As of December 13, 2020, the bitcoin blockchain will have grown to 308 gigabytes (GB), a significant increase from the 4.52GB in December 2012. The result is that a block represents a page in a record book or ledger. After a block is deemed 'complete,' the blockchain moves on to the next block. The block acts as a repository for immutable data that cannot be modified or destroyed once it is formed.

In Bitcoin, a block is a fundamental component of the blockchain, the decentralized ledger that records all transactions within the Bitcoin network. A Bitcoin block is a collection of data containing information about multiple transactions. Each block is linked to the previous one through a cryptographic hash, forming a chain of blocks—hence the term "blockchain."

The structure of a Bitcoin block includes several key elements. The block header comprises metadata such as a timestamp, a reference to the previous block's hash, a nonce (a number used in the proof-of-work consensus algorithm), and the Merkle root, a hash of all the transactions in the block. The block also contains a list of individual transactions, each with details like the sender's and recipient's Bitcoin addresses, the amount transferred, and a digital signature.

Miners play a pivotal role in the creation of Bitcoin blocks. They compete to solve complex mathematical problems through the proof-of-work mechanism, and the first one to solve the puzzle gets the right to add a new block to the blockchain. This process ensures the security and immutability of the transaction history. As the blockchain grows with each added block, it forms a transparent and tamper-resistant record of all Bitcoin transactions since its inception.