A blockchain is an open digital ledger that records transactions, which can never be altered or reversed once recorded, and accessible by anyone with an internet connection. The entire list of transactions, or events is called the chain and every change to the list is a block.
Unlike traditional databases which are owned by institutions, such as banks and governments, a blockchain doesn’t belong to anyone, it exists simultaneously across a large network of computers.
A blockchain is typically managed by a peer-to-peer network, collectively adhering to a protocol for validating new blocks. By design, blockchains are inherently resistant to modification of the data. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks and a collusion of the network majority, making this virtually impossible.