When you search about blockchain the most repited definition can be seen is " A blockchain , originally block chain , is a growing list of records , called blocks , which are linked using cryptography ."- by Wikipedia. But what actually these blocks contain and how it is linked and other technical stuffs are not shown in simple way. These blocks contain data which includes some parameters like the number of block, previous hash etc. which are needed to calculate the hash of present block. There are mainly five things to understand what actually the tech is. 1- Hash cryptography 2- Distributed P2P network 3- Immutable ledger 4- Consensus Protocol 5- Mining Each of these points are explained in next blogs but in simple way.