The four strangers in this example represent the blockchain’s community of users. We are using strangers to explain this, because in the real world, most blockchain users do not know each other.



The notebooks in this example are the blockchain itself. The blockchain stores a public record of every single transaction ever made on it. The blockchain is not on paper – it's 100% digital and public.



Most importantly, there are thousands and thousands of identical copies of the blockchain held by users around the world. All these copies are kept in sync by the system that runs the blockchain.