Blockchain, or distributed ledger technology, is a database that is consensually shared, replicated, and synchronized.
The replication and storage of transactional data by each party, or node, on a blockchain network is known as a distributed ledger. Conﬂicts, or inaccuracies within the database, are automatically resolved with predeﬁned ledger rules.
Blockchains, while similar to databases, are not used for general data storage, but rather hold information about transactions. Sometimes the blockchain will contain the transactions themselves or may include the proof a transaction is valid.
Operation with peer-to-peer networks,
Decentralized transaction record keeping,
Consensus or trust-based transactions,
Large distributed blockchains are available for anyone to participate in and are generally open-sourced with the code maintained by a broad community. For example, Bitcoin, one of the most commonly known blockchain networks, is a public blockchain.
Large distributed blockchain network with established roles that individuals can ﬁll when using the blockchain. For example, a group of banks may share sensitive cash reserve information with each other through the blockchain.
Oftentimes a smaller blockchain is tightly controlled and is established between trusted entities that wish to share sensitive information. For example, an organization could use an internal blockchain to certify documents for its own use.