Blockchain technology is a decentralized, distributed digital ledger system that securely records and stores transaction data across multiple computers. It is powered by a peer to peer network of computers connected together in a distributed and decentralized manner, eliminating the need for a centralized authority or server. Bitcoin and other cryptocurrencies use blockchain technology to transact in a secure and anonymous way. Transactions are recorded on blocks, which are cryptographically linked together in a chain, forming the blockchain. Each block contains a cryptographic hash of the previous block, a timestamp and transaction data. The cryptographic hash ensures that any change to the data will be immediately noticed.