Block (Blockchain)

A block is a container of data in a blockchain. It usually holds a list of recent transactions, a timestamp, a reference to the previous block, and other metadata needed by the network. Because each block points back to the one before it, the blocks form an ordered chain. This structure helps make the transaction history difficult to alter: changing an old block would also affect the links that come after it.

Blocks matter because they are how a blockchain records and organizes activity. Depending on the network, validators or miners propose new blocks, and the rest of the network checks that the included transactions follow the rules, such as not spending the same coins twice. For example, instead of every Bitcoin payment being written to the ledger one by one in isolation, many payments are grouped into a block, confirmed together, and then added to the shared record.