Blockchain

A blockchain is a distributed digital ledger that records transactions across a network of computers instead of a single central server. Each new batch of transactions, called a block, is cryptographically linked to the one before it, making the history extremely difficult to alter after the fact. Because every participating computer (node) holds a copy of the same ledger, no single party controls or can quietly rewrite it. Bitcoin and Ethereum are the best-known examples, but the same technology underpins thousands of other cryptocurrencies and applications.