What is DeFi?
Lesson 29 · practical guide
Decentralised finance uses smart contracts and blockchains for swaps, lending and liquidity without a traditional intermediary. Removing an intermediary changes risk; it does not remove it.
What you will learn
Understand DeFi as software that moves value through smart contracts, with risks different from a bank.
Key terms
- Smart contract — program code that executes rules on a blockchain.
- Protocol — a set of contracts and interfaces designed for a financial function.
- Oracle — a mechanism that brings external data, such as a price, into a contract.
Follow these steps
- Identify the contract addresses, admin powers, upgrade process and audit limitations.
- Understand where yield comes from: fees, incentives, borrowing interest or token issuance.
- Model smart-contract, oracle, liquidity, bridge, governance and stablecoin failure.
- Test with a small amount and review permissions and exit liquidity before depositing.
Practical advice
DeFi removes some intermediaries but does not remove risk. Code can be exploited, liquidity can disappear and a high displayed yield may be mostly newly issued tokens.
Long-form explainer
The full guide
Read this lesson as a chapter: understand the mechanism, test the assumptions and apply the idea with a clear risk limit.
DeFi is software-mediated finance
A decentralised-finance application usually combines smart contracts, tokens, interfaces and data sources to perform a function such as swapping, lending or providing liquidity. There may be no bank deciding each transaction, but the user still relies on code, governance, oracles, network infrastructure and the economic incentives of participants.
A contract can execute exactly as written and still create a bad outcome if the code contains a bug or the input data is manipulated. An audit can identify issues but cannot prove that a system is safe. The absence of a central operator does not mean the absence of risk.
Map the trust assumptions
Before connecting a wallet, identify what the contract can do, who can upgrade or pause it, how prices enter the system and what happens if liquidity disappears. Check the chain, domain, contract address, permissions, fees and withdrawal path. Read documentation, but compare it with the actual on-chain configuration when possible.
Start with a small transaction and avoid granting more permission than necessary. Keep a record of approvals and revoke unused ones. Treat yield, governance tokens and attractive incentives as compensation for risk, not as free money.
What usually goes wrong
The first mistake is treating decentralisation as safety. Removing an intermediary removes that intermediary's failure modes and adds different ones: contract bugs, oracle manipulation, governance capture, upgrade keys held by a small group and liquidity that can vanish. The second is trusting an audit as if it were a guarantee. An audit is a review at a point in time, with a defined scope, by people who can miss things; code can also be perfectly correct while the economic design is broken.
People also ignore the layers underneath. A position may depend on a front end, a router, several contracts, a price oracle, a bridge and a stablecoin, and it is only as reliable as the weakest of them. The final error is assuming the exit will work when it is needed. Yields and deposits usually function smoothly in calm conditions; the relevant question is what happens when everyone withdraws at once, gas costs spike and liquidity thins. Test a small withdrawal early rather than discovering the answer with a full position during an incident.
How it works
Understand the contract, assets, oracle, admin keys, fees, liquidation and liquidity before connecting a wallet. Audits can find some bugs but do not guarantee safety, honest governance or sustainable economics.
Risks include code bugs, oracle manipulation, bridge failure, impermanent loss, bad debt, governance attacks, front-running, phishing and irreversible transactions. Read documentation and test with a small amount.
Worked example
Numbers make an idea concrete. Here is a small, illustrative one — not a forecast.
A lending protocol may liquidate collateral when a health threshold is crossed. An oracle failure or sudden move can make liquidation occur at a poor price.
Before you act
Run through these questions before you commit any money or make a decision based on this lesson:
- What contract and address will I use?
- Who can upgrade or pause it?
- What if oracle or liquidity fails?
- What is the complete worst-case loss?
Practice this lesson
Reading is a start; doing the exercise is what makes the idea stick.
Map one protocol’s funds, price feeds, admin powers, withdrawal path, fees and failure mode. If you cannot trace the flow, do not deposit.
Further reading
Educational content only: This guide is not personal financial, legal or tax advice. Markets involve risk, including the possible loss of capital. Verify current rules, fees and product availability in your country.