A blockchain is a technology that enables records of monetary transactions (called “blocks”) to be transferred across many computers, which cannot be altered retroactively without altering the subsequent blocks. They are typically managed by a peer-to-peer network that decides by consensus to alter a block, making blockchains secure by design.
Blockchains were invented in 2008 to serve as a public transaction ledger of Bitcoin. For learners interested in cryptocurrencies, blockchains are important to learn about due to their role in solving the need for a trusted authority or central server to manage flaws in digital cash transactions.