Bitcoin is a decentralized digital currency. Decentralized means that all transactions are made directly between users without any agents, like banks, payment systems, and without government control. Digital means that Bitcoin exists as a recording of transaction data. The data is recorded in blocks and the system of all blocks is called blockchain. This technology is the basis of Bitcoin, other digital currencies and blockchain-platforms. Each block is the result of calculations — a certain algorithm necessary to record information in the block. These calculations are carried out by miners, who create new blocks and receive a reward for that. The whole blockchain is located on every user device, So there’s no way someone can hack this distributed database unless they can access hundreds of thousands of devices at the same time.