A block chain is a chain of blocks strung together. Each block contains the details of several transactions. You can therefore trace back exactly which way a transfer was made. The block chain is the general ledger of a crypto currency, in which all transactions are recorded exactly. The miners permanently add further blocks to the block chain, in which new transactions are recorded.
To prevent fraud, all miners synchronize their block chain with each other. This ensures that nobody can spend the same amount more than once. The transfer is only considered to be completed when several miners have confirmed it.
This ensures that the block chain is synchronized everywhere and that nobody cheated. This is why crypto currencies are called decentralized systems. Here there is no central institution like a bank, which supervises the transfers. Instead, this activity is performed decentrally by all miners.
The principle of block chaining is therefore also considered to be groundbreaking and visionary; more and more companies (insurance companies, energy, medicine) want to use it in the next few years.
