Blockchain technology is a decentralized digital ledger that records transactions across many computers. This ensures that the recorded transactions cannot be altered retroactively, providing security and transparency. Each block in the chain contains a number of transactions, and every time a new transaction occurs, a record of that transaction is added to every participant's ledger. The technology underpins cryptocurrencies like Bitcoin and Ethereum, enabling peer-to-peer transactions without the need for intermediaries. Its applications extend beyond finance, impacting sectors such as supply chain management, healthcare, and voting systems, where trust and verification are crucial.