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# System prepended metadata

title: Blockchain

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# Blockchain
A blockchain is a decentralized, distributed, and timestamped database. Each record in the database is known as a [block](https://hackmd.io/i96lV8wuSbuTTXG4ZM1NHQ), and the database is commonly referred to as a [ledger](https://hackmd.io/996WvpZ3QUOOgByRqSutMg). 

The blocks in the ledger are linked to one another using [cryptography](https://hackmd.io/ncPTp-k7Sfi_Om1sFPrqjg), and are  immutable, contain a [hash](https://hackmd.io/ZUr5V-sTSnG6kba15flVzw) of the previous block, a [timestamp](https://hackmd.io/K2KWq6rOT0CnU44AKWhz6w), and transaction data.