The technology that underpins the Bitcoin cryptocurrency and allows for secure transactions is called blockchain. Blockchain is a decentralized and distributed digital ledger that records all transactions across a network of computers in a secure and transparent manner. Each block contains a list of transactions and is linked to the previous block, forming a chain. This structure ensures data integrity and prevents unauthorized alterations, making blockchain a foundational technology not only for cryptocurrencies but also for various applications in finance, logistics, and more.