A blockchain is a digital ledger that is shared across a computer centric network and securely connected together using cryptography. It is made up of special ledger records called blocks. Each block is made up of a list of transactions.
Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data. This design makes blockchain records resistant to modification — once data is recorded, it cannot be altered retroactively without altering all subsequent blocks and obtaining consensus from the network.
Blockchain technology underpins cryptocurrencies like Bitcoin and Ethereum, but its applications extend far beyond digital currency — to supply chain management, healthcare records, voting systems, and more.