The book details the technical concepts of blockchain technology, such as peer-to-peer and distributed systems, data structures, transactions, cryptography and hash values, system integrity, and consensus building in a distributed environment. The book is written in a dialogue style, without the use of computer and mathematical jargon. The material is presented in a step-by-step, logically connected manner, which allows you to consistently, level by level, increase knowledge about blockchain technology. Numerous examples, analogies and metaphors help to better understand how blockchain systems work, even for those who did not know anything about it before.The publication is intended for a wide range of readers with different levels of technical knowledge who want to understand what what is blockchain.