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03 — Crypto & Web3 · Core

DeFi: Lending, Exchanges & Yield

CTRT Learn · Core · 13 min read

DeFi is where smart contracts meet money at scale. It recreates the core services of the financial system — lending, trading, earning interest — as open programs that run without banks or brokers. Anyone with a wallet can use them, permissionlessly, from anywhere. It's one of the most genuinely innovative and most dangerous corners of crypto. This lesson explains how it works and where the risks hide.

What makes it "decentralized"

In traditional finance, a bank holds your money and processes your transactions; you trust the institution. In DeFi, those functions are performed by smart contracts (from the Ethereum course) that anyone can inspect and use. There's no application form, no approval, no intermediary taking custody. You connect your wallet, interact directly with the code, and your assets stay under your control until the moment a transaction executes. The trust shifts from a company to transparent, auditable software — which is powerful when the code is sound and catastrophic when it isn't.

Decentralized exchanges (DEXs)

A decentralized exchange lets people trade one token for another without a company holding their funds or matching orders. Most use an elegant invention called the automated market maker (AMM): instead of matching buyers and sellers, users trade against a liquidity pool — a smart contract holding a reserve of two tokens. A formula automatically sets the price based on the ratio in the pool. Anyone can become a liquidity provider by depositing tokens into the pool, earning a share of the trading fees in return. It's a marketplace that runs entirely on code.

Lending and borrowing

DeFi lending protocols let people earn interest by lending out their crypto, and others borrow against collateral — all without a bank. Lenders deposit assets into a pool and earn yield; borrowers take loans from that pool. The key difference from traditional lending is that DeFi loans are almost always over-collateralized: to borrow $100, you must lock up more than $100 of other crypto. This compensates for there being no credit checks or legal recourse — if your collateral's value falls too far, the smart contract automatically liquidates it to repay the loan. It's lending enforced entirely by code and collateral.

Yield: where do the returns come from?

DeFi is famous for attractive yields, and the most important question to ask is always where the yield comes from. Legitimate sources include:

• Trading fees earned by providing liquidity to exchanges.
• Interest paid by borrowers in lending protocols.
• Token incentives — protocols handing out their own tokens to attract users (often temporary and inflationary).

The discipline from the Markets track applies fully: high yield means high risk. A "20% stablecoin yield" is not free money — it's payment for a risk you may not have identified. If you can't explain where a yield comes from, assume you are the risk.

The risks, honestly

DeFi's openness removes some risks and adds others that are easy to overlook:

• Smart contract risk — a bug or exploit in the code can drain funds instantly and irreversibly. This has cost billions.
• Liquidation risk — borrowers can be wiped out fast if collateral drops in a volatile market.
• Impermanent loss — liquidity providers can end up worse off than simply holding, when pool prices move apart.
• Oracle and dependency risk — protocols rely on price feeds and other protocols; one failure can cascade.
• No safety net — there's no deposit insurance, no customer support, and no one to reverse a mistake or theft.

Why it matters

DeFi is a live experiment in rebuilding finance as open infrastructure — composable, global, and permissionless, where protocols snap together like building blocks. Its potential is real: financial services for anyone, transparent by default, without gatekeepers. So are its dangers, which is exactly why disciplined risk management — the heart of the Markets track and of how CTRT operates — matters even more here than in traditional finance. In DeFi, you are your own bank, with all the freedom and all the responsibility that implies.

Key terms

• DeFi — financial services rebuilt as open smart contracts.
• DEX / AMM — a decentralized exchange using liquidity pools, not order books.
• Liquidity pool — a contract of pooled tokens that trades and earns fees.
• Over-collateralization — locking up more value than you borrow.
• Smart contract risk — the danger of bugs or exploits in the code.

Next course — Privacy & Sovereign Money →

CTRT Learn is general education, not financial, legal, or tax advice. Nothing here is a recommendation to buy or sell any asset. Digital assets are volatile and may result in total loss of capital. CTRT is operated by Centrente, part of the Trancent world.