## Summary

Now you should understand the basic components of a blockchain. Blocks are groups of transactions grouped together and act as the fundamental unit of a blockchain. Miners are computers that create new blocks on PoW blockchains. Validators, also called witnesses and other names, are computers that create blocks on PoS blockchains. Digital signatures are composed of public and private keys and use mathematics to prove the author of the data.

The key idea of hashing is to use a mathematical function that maps arbitrary data to a single, simple to deal with value. Any change to the data will make the end value very different

- It's essentially impossible to construct the original data from the hash, but it's easy to create the hash from the original data
- You can use these properties to prove that data has not been changed

In the next chapter, we will learn what these systems are and how blockchain counts as both. We will learn how to differentiate between the two systems and why these concepts...