Module 00 — Fundamentals: what crypto is and why it exists

Goal: understand what problem Bitcoin solves, what a blockchain is at a conceptual level, and get to know the main categories of crypto assets. Without this, everything else is just numbers on a screen.

🔊 Listen to this module (Spanish audio, 6 min 47 s)

Narrated version of the full module — perfect for reviewing while doing something else.

1. The problem Bitcoin solves

Before 2009, all digital money needed a trusted intermediary (a bank, PayPal, Visa) to prevent double spending: someone spending the same money twice. A digital file can be copied for free; so how do you stop someone from "copying" their digital euros?

Bitcoin (Satoshi Nakamoto's whitepaper, 2008) solved double spending without an intermediary: a network of thousands of computers keeps a shared ledger (the blockchain) and agrees on which transactions are valid through a consensus mechanism.

What matters for an investor: Bitcoin is money that no one can print at will (maximum supply: 21 million), no one can censor, and no one can confiscate if you safeguard your keys properly. That is its investment thesis: "digital gold".

⚠️ Holding crypto on an exchange is NOT the same as owning it

When you buy BTC on an exchange (Binance, Coinbase…), the exchange holds the keys for you. You only see a number on the screen, exactly like the balance in your bank app: it's an entry they owe you (an IOU), not coins you control yourself.

That's why, as long as your crypto stays on the exchange, you do NOT enjoy the properties from section 1 (uncensorable, non-confiscatable). The exchange can:

• Freeze your account or ask you for extra paperwork before letting you move anything.
• Block withdrawals (sometimes from one day to the next).
• Go bankrupt and leave you without your funds.

Hence the sector's most repeated principle: "not your keys, not your coins" (if you don't control the keys, you don't control the coins).

What actually happened:

• FTX (November 2022): one of the largest exchanges in the world collapsed suddenly. Hundreds of thousands of users had their withdrawals blocked and could not get their money back, even though they saw it in their balance the day before.
• Mt. Gox (2014): the biggest Bitcoin exchange of its time collapsed after losing ~850,000 BTC. More than ten years later many users are still waiting to get part of it back.

Practical rule: to start trading it's totally normal to use an exchange (it's the easiest way to buy your first BTC). But anything you want to HOLD long term should move out to your own wallet where YOU hold the seed phrase. You'll learn that in module 01.

2. Blockchain in 5 concepts

1. Transaction: "address A sends 0.1 BTC to address B", cryptographically signed with A's private key.
2. Block: a package of grouped transactions. Each block references the previous one through its hash → chain of blocks.
3. Hash: a digital fingerprint of data. Change a single comma in the block and the whole hash changes. That's why it's tamper-proof: altering an old block invalidates all the following ones.
4. Consensus: how thousands of nodes agree on which chain is the valid one.
5. Proof of Work (PoW) — Bitcoin: miners compete by spending electricity to add blocks. Security = the energy cost of attacking the network.
6. Proof of Stake (PoS) — Ethereum (since 2022): validators lock up capital (32 ETH) as collateral. If they cheat, they lose it (slashing).
7. Private key / public key: the private one signs (it's your master password, NEVER share it); the public one generates your address (you share it to receive funds).

⚠️ The rule that saves your money: never share your seed phrase

When you create your first wallet (module 01) you'll receive a phrase of 12 to 24 words (the seed phrase). THAT phrase IS your private key in readable form: whoever has it, has your money. So:

• NO legitimate party will ever ask you for it: not Binance "support", not a Telegram admin, not an Elon Musk "giveaway", not a website to "validate/sync your wallet". If anyone asks you for it, it's 100% a scam.
• Never type it into any website, chat app, photo, or cloud file. Only on paper, by hand, stored physically.
• There's no "I forgot my password": if you lose it, you lose your funds forever. If you leak it, your account is drained in seconds and it's irreversible (there's no bank to refund you).

This is the #1 cause of total capital loss in crypto. Module 01 teaches you how to safeguard it properly.

3. The main assets

Category	Examples	Thesis / use
Bitcoin (BTC)	BTC	Store of value, "digital gold", fixed supply
Smart contract platforms	ETH, SOL, AVAX	Platforms where applications run (DeFi, NFTs). Their value depends on the activity they host
Stablecoins	USDT, USDC, DAI	Worth ~1 USD. A safe haven within the ecosystem, the main trading pair
DeFi tokens	UNI, AAVE, LDO	Govern/capture value from decentralized financial protocols
Memecoins	DOGE, SHIB, PEPE	No utility. Pure speculation and community. Extreme risk
Everything else ("altcoins")	thousands	90%+ go to zero in the long run. Maximum caution

💵 A stablecoin is NOT a bank: it can break its peg (depeg)

The fact that a stablecoin "is worth ~1 USD" is a promise, not a law of physics. The price holds at one dollar because behind it there's some backing or a mechanism that sustains it… and that backing or mechanism can fail. When it breaks, the coin is said to depeg (lose its peg).

There are two very different types:

• Backed / collateralized (USDC, USDT): there are real dollars (or equivalent assets) held in reserve backing every token. It's like a coat check: you leave your coat and get a ticket; the ticket is worth something because the coat is there in storage. These are the most solid, but not 100% risk-free (it depends on whoever holds the dollars not going bankrupt).
• Algorithmic (the UST case): they hold the price with code and confidence, with no real dollars behind them. These are the most fragile. AVOID THEM as a beginner.

What actually happened:

• UST / Luna (May 2022): an algorithmic stablecoin worth ~1 USD collapsed to nearly 0 in a few days. About 40 billion dollars evaporated. Many people who thought they were "safe in stablecoins" lost everything.
• USDC (March 2023): a backed stablecoin, one of the most reputable, temporarily dropped to 0.87 USD because part of its reserves were in Silicon Valley Bank, which collapsed. It recovered its peg days later, but it scared the whole market and proved that even the "good ones" aren't untouchable.

Practical rule for you: only use large, backed stablecoins (USDC, USDT) and only as a trading pair (to enter and exit positions), not as a long-term safe. Never assume that "being in stablecoin" = zero risk. A stablecoin is not the same as having euros in the bank: there's no deposit guarantee and no one to refund you if it depegs.

Smart contracts (the bare minimum you need)

A smart contract is code published on a blockchain that runs automatically: "if X happens, transfer Y". Ethereum popularized it. All of DeFi (module 6) is smart contracts. For an investor: more contract activity on a network = more demand for its native token (to pay fees, "gas").

4. Crypto market cycles

Crypto has historically moved in cycles of ~4 years, correlated with Bitcoin's halving (every ~4 years the issuance of new BTC is cut in half: 2012, 2016, 2020, 2024…).

Historical pattern (not a future guarantee): - Bull market: 12-18 months of strong gains after the halving. Euphoria, everything goes up, memecoins do 100x. - Bear market: drops of 70-90% from the highs. Lasts 1-2 years. Weak projects die. - Accumulation: boring sideways action. Historically, the best time to buy and the one fewest people take advantage of.

The halving is NOT a magic up button

Only 3-4 halvings have happened in all of history (2012, 2016, 2020, 2024). With so few cases, you CANNOT claim that "after the halving the price goes up": it's like flipping a coin 3 times, getting heads all 3 times, and concluding the coin always lands heads. Maybe the pattern repeats, maybe it doesn't. On top of that, each cycle has been LESS explosive than the last (the 2024 rise was much smaller in % than the 2017 one), so copying what worked "last time" usually fails. If someone tells you "buy now, the post-halving bull is coming for sure", be suspicious: nobody knows the future, and anyone who claims it with certainty is either fooling themselves or wants to sell you something. Never put in money you can't afford to lose based on this pattern.

Key lesson: most retail money enters during the euphoria (at the top) and sells in the panic (at the bottom). Your job in this course is to not be that retail investor.

5. Where to look at data (free)

• CoinGecko / CoinMarketCap — prices, market cap, supply, rankings.
• TradingView — charts (you'll use it in module 4).
• mempool.space — Bitcoin explorer: watch real transactions live.
• etherscan.io — Ethereum explorer.

Exercises

1. Open mempool.space and watch blocks coming in in real time. Identify: block number, number of transactions, average fee.
2. On CoinGecko, look up the market cap of BTC, ETH and USDT. Calculate what % of the total market BTC represents (that's called BTC dominance).
3. Find the historical BTC chart since 2013. Visually identify the 4 cycles (peaks: 2013, 2017, 2021, 2024-25) and measure how much it fell from each peak to the next bottom.
4. Read the Bitcoin whitepaper (9 pages). You don't need to understand it all; just take in the introduction and the conclusion.

Checkpoint ✅

Answer without looking: 1. What problem does a blockchain's consensus solve, and why weren't banks a sufficient solution? 2. What's the difference between a private key and a public address? 3. Why is the fixed supply of 21M central to BTC's thesis? 4. What is a stablecoin and what does a trader use it for? - Why is a stablecoin not the same as having euros in the bank? 5. What has historically happened to BTC's price after each halving, and why does that NOT guarantee it will repeat? 6. If someone from your exchange's "support" asks you for your seed phrase to "fix a problem", what do you do and why? 7. If you buy BTC on Binance, do you really "own" BTC? Which property from section 1 do you lose, and why?

→ Next: Module 01 — Security and wallets