Blockchain

What Blockchain means

A blockchain is a database that many independent parties maintain without trusting one another. Transactions are grouped into blocks, and each block contains a cryptographic hash of the one before it, so the chain forms a tamper-evident sequence: altering an old block changes its hash and invalidates every block after it. Copies of the ledger are held by nodes worldwide, and a consensus mechanism such as proof of work or proof of stake determines which participant may add the next block and how disagreements are resolved.

The design gives specific properties. Anyone can verify the full history independently rather than trusting an operator's statement, settlement is final once a transaction is buried under enough subsequent blocks, and no single party can unilaterally reverse a confirmed transfer or censor the ledger as a whole. Public chains are open to anyone; permissioned chains restrict who may validate and are used in enterprise settings where the participants are known and full decentralisation is not the objective.

The trade-offs are real and often understated. Every node processing every transaction limits throughput, which is why public chains are slower and more expensive per transaction than a centralised system and why layer-two networks exist to batch activity. Immutability cuts both ways: a mistaken transfer or a stolen key cannot be undone by an appeal to anyone. Decentralisation also varies enormously between chains, and a network with few validators or concentrated stake offers considerably weaker guarantees than the label implies.