Blockchain
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def
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a decentralized, distributed public ledger of transactions, with no single point of authority — everyone on the network maintains and replicates the ledges
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how it works (step by step)
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a transaction is requested (transferring cryptocurrency, medical records, a data backup, a house title, etc.)
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the transaction is sent to every node in the decentralized network to be verified
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the verified transaction is added to a new block, along with other recently verified transactions
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a hash is calculated from the previous blocks in the chain and added to the new block
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the block is appended to the end of the blockchain, which is then updated across all nodes
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if any block is altered, its hash — and every hash that follows it in the chain — must be recalculated; the altered chain will no longer match the copies held by the rest of the network, and gets rejected
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strength
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decentralization means there's no single point of failure to attack — an adversary would need to take over a majority of the network's nodes to rewrite transaction history (difficult, though not impossible; this has happened on some smaller cryptocurrency networks)
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common use
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payment processing, digital identification, supply chain monitoring, digital voting, and more — cryptocurrency (e.g., Bitcoin) is the most common use, but not the only one
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