The technology that underpins cryptocurrencies like Bitcoin is called blockchain. Blockchain is a decentralized, distributed ledger technology that securely records transactions across multiple computers. Each block in the chain contains a list of transactions and is linked to the previous block, forming a secure chain. This structure ensures transparency, security, and resistance to fraud and tampering. Additionally, cryptocurrencies utilize cryptographic techniques for securing transactions and controlling the creation of new units. The decentralized nature of blockchain eliminates the need for central authorities, promoting peer-to-peer transactions and increasing user privacy.