Original Youtube video: https://youtu.be/kHybf1aC-jE

Hey, I’m back!

In this lesson I’m going to explain what a blockchain is. You’ll have to grant me some patience as entire books have been written about this topic.

First off, I’m going to break it down into 2 sections.

1) What are blocks?

When it comes to a blockchain, the blocks are what makes it up.

Simply put, blocks are just a collection of data.

In terms of Bitcoin, this data is transactions from one account to another account.

In terms of Ethereum, it’s transactions AND Smart Contracts (the next lesson!).

Blocks are usually not that big, and how fast they are created is determined by the blockchain.

Bitcoin’s ‘block time’ is 10 minutes.

Ethereum’s ‘block time’ is 10 seconds.

2) What’s the chain part?

Every block starts with a very important piece of data.

A summary of the last block.

After the summary, they include their data, and then they summarize the summary + new data.

I know this is confusing, but here’s a picture to help:

[image to be added of 3 blocks, using math]

In this picture, I’m using numbers as the ‘summaries’, because the summaries are actually really messy mixes of numbers and letters. They use math to ‘summarize’ the data. Here’s what a usual summary looks like: “0xe8e341827a0b434690863b14a6b29ba597c77ab49062dbf7164c72b1cc7bb2aa”

This way, every block has a summary of each block before it.

If you want to go back 30 blocks and change something, you would be changing 30 summaries.

I’m trying to tell you that you CAN’T go back and change something.

If you did, everyone else who has the ledger could instantly see that you have a bunch of fake summaries.

So, in short, blockchains are simply a collection of information that can’t be tampered with once it’s in a block.

We could store pictures, videos, Wikipedia, or even a diary on a blockchain.

However, it’s most useful when we use it to store financial data!

I hope this helped you understand what a blockchain is, but feel free to reach out if you have any questions!

– Theodore