Blockchain
A shared, tamper-evident ledger of records stored on many computers at once — the base layer under all cryptocurrencies and Web3 apps.
A blockchain is a growing list of records, called blocks, linked together with cryptography. Each block references the one before it, so changing an old record would require rewriting every later block on thousands of machines at once.
Why it exists
Before blockchains, digital money always depended on a trusted middleman to keep the ledger. A blockchain removes that trust requirement: the protocol itself, verified by the whole network, becomes the source of truth.
Public vs private
Public blockchains like Bitcoin and Ethereum are open to anyone — read a balance, send a transaction, or run a node. Private or “permissioned” versions are often run by companies and don’t act as censorship-resistant networks. W3D only scores public networks.
Related terms
Bitcoin, Node, Consensus Mechanism, Layer 1, Decentralization, Hash