"Like the Internet itself, which no single entity “owns,” blockchain technology can be thought of as enabling an open, distributed, yet secure database or accounting ledger — owned by no single site, but available equally to its participants — for recording transactions.
Running on a network of nodes over the Internet, blockchain networks can be public, private, or consortium-based (i.e., hybrid). Blockchain networks use cryptographic methods to maintain the security and privacy of the distributed ledger.
Participants in a blockchain ledger can submit transactions to add, remove, or modify records in the database according 7 to a set of rules that are guaranteed to be enforced by the ledger itself.
Once a transaction is accepted into the blockchain and recorded in the ledger, the data becomes immutable and cannot be tampered with, revised, or repudiated. This is one of the key characteristics of the blockchain."