A blockchain is a type of distributed digital ledger that stores data in blocks linked together in a chronological chain. Each block contains a set of transactions, a timestamp, and a unique cryptographic code called a hash that connects it to the previous block. This structure makes it virtually impossible to alter past records without changing every subsequent block.
Unlike traditional databases controlled by a single company or institution, a blockchain is maintained by a decentralized network of computers (called nodes). Every node holds a copy of the entire ledger, and new transactions must be verified by the network before they are added. This process is governed by consensus mechanisms such as Proof of Work or Proof of Stake.
Key properties of blockchain technology include:
- Transparency – All transactions are publicly visible on the ledger.
- Immutability – Once confirmed, data cannot be easily changed or deleted.
- Security – Cryptographic hashing protects the integrity of the data.
- Decentralization – No single point of failure or control.
Blockchains power cryptocurrencies like Bitcoin and Ethereum, but they are also used in supply-chain management, healthcare records, voting systems, and more. The technology is the foundation of the entire crypto ecosystem, including decentralized finance (DeFi) and NFTs.