# Summary
This chapter introduced us to the very basics of blockchain and why it is useful. What
we learned in this chapter will form the basis of our understanding of the blockchain.
* Systems are a crucial part of the computer world. They are divided into three main types
all of which have their benefits and drawbacks.
* Distributed systems' flaw can be expressed in a theoretical problem known as the *Byzantine
General's Problem* which highlights the difficulty of cooperating in a system where nodes
don't trust each other.
* Blockchain is a solution to the Byzantines General Problem through a network that shares a
unique blockchain data structure, *BADS*.
* *BADS* is an add-only singly-linked list where the nodes are blocks and data in blocks is arranged by Merkle Trees.
* Blocks are composed of the data they store and a block header.
* The block header contains information about the block.
* Participants in the blockchain network verify all data independently and trust the system and that a majority of other participants are honest.
* The above allows any node to work in a *trustless* system where it doesn't need to 
trust any one particular participant, just the network as a whole.