Before moving on to a detailed and more technical explanation of Bitcoin mining, I'd like to give you an overview of the principle, which is deliberately simple and schematic. If you already have some basic knowledge, you can go straight to the heart of the matter in the next chapter, after answering the quiz questions. This chapter is aimed primarily at beginners, to give you a gentle start.

Imagine Bitcoin as a large public notebook, shared by everyone, where we write down who sent bitcoins to whom. This notebook is called the blockchain. It can't be held by just one person, otherwise it would have to be trusted. Instead, Bitcoin works collectively: thousands of computers verify and maintain the same version of this notebook.

In Bitcoin, when you make a payment, you create a transaction. This transaction is not instantly added to the notebook. It is first sent to the network, then waits to be integrated into the next transaction packet. This packet is called a block.

A block is simply a set of transactions grouped together. When a block is ready, it's not enough to publish it. You have to prove to the network that the block is worthy of being added to the shared ledger. This is where mining comes in.

Mining is the work of validating a block by consuming energy. Actors called miners use specialized computers. These machines consume electricity to carry out a very large number of tests, in a loop, until they find a proof that the network accepts. When a miner finds this proof, his block is considered valid.

Once the block has been validated, it is broadcast to the network. The other nodes quickly check that it complies with the rules, then add it to the sequence of previous blocks. This is why it's called a "blockchain": each new block comes after the others, in sequential order, and this chain grows little by little.

To sum up, transactions are first created. Then, they are grouped together in a block. Then, a miner validates this block by consuming electricity. Finally, this block is added to the blockchain, and the transactions it contains become confirmed.

If miners consume electricity, it's not because they're volunteers. They do it because there's a reward. When a miner validates a block, he receives two types of income. On the one hand, he receives newly created bitcoins. On the other, he collects the fees paid by users for the transactions included in the block. In other words, the miner is compensated both through programmed monetary issuance, and by transaction fees determined by a market.

At this stage, you're deliberately given a very simple view of mining. It doesn't yet explain how the block is constructed in detail, or how exactly the proof miners are looking for works, or how Bitcoin keeps a steady pace, or how the reward is calculated precisely, or how it's claimed. That's okay, that's all we're going to see in the rest of this MIN 101 course!

The aim of this chapter was simply to give you a clear mental structure: transactions → blocks → mining → blockchain → reward. Keep this chain of ideas in mind. In the rest of the course, each chapter will add a layer of technical detail on one of these elements, until you understand not only what's going on, but how and why it works reliably, at scale, without a boss, and without needing trust.