Blockchain

A blockchain is a database structured as a chain of blocks. Each block bundles together a batch of transactions and includes a cryptographic reference to the block before it. Because every block points back to its predecessor, changing an old record would break the links that follow — a property that makes the history practically tamper-evident. Rather than living on a single company's server, the ledger is copied across many independent computers, called nodes, that each hold a full record.

The close-up (near lens): New transactions are grouped, verified, and added to the chain according to a shared set of rules. Participants reach agreement on which version of the ledger is correct through a consensus mechanism, and cryptographic signatures confirm that a transaction was authorized by the rightful owner. Once data is added and confirmed by the network, it is designed to be permanent.

The wide shot (far lens): The deeper idea is coordination without a central gatekeeper. A blockchain lets strangers share one trusted record of who owns what, without relying on a single bank or intermediary to keep the books. This foundation supports cryptocurrencies, smart contracts, and other applications. Different networks make different trade-offs between speed, cost, openness, and decentralization — there is no single "best" design. This is informational only; always do your own research.