What Is DeFi? Finance Without Intermediaries, and Its Risks
Lesson 1 of 10 · Beginner
What is DeFi? A simple definition
DeFi, short for Decentralized Finance, is a set of financial services that run on a blockchain through smart contracts instead of through a bank, exchange or broker. A smart contract is a program deployed on a network such as Ethereum that anyone with a wallet can call. Its rules are written in code, and anyone can read them.
In a bank, staff, ledgers and regulations decide where your money goes. In DeFi, code plays that role. When you swap one token for another on a decentralised exchange, nobody “approves” your order. You sign a transaction, the contract executes it according to its formula, and the result is recorded in the next block.
The main DeFi services are roughly the familiar financial ones, just with a different mechanism:
- Trading and swapping: decentralised exchanges (DEXs) that, instead of an order book, often use a liquidity pool.
- Lending and borrowing: protocols where you deposit assets and borrow against them or earn interest.
- Stablecoins: tokens that are meant to stay pegged to the dollar or another asset.
- Derivatives: perpetual contracts and options on a blockchain.
- Staking and asset management: locking tokens to secure a network, or depositing into vaults that run automated strategies.
Three features that make DeFi different
1. Permissionless. At the contract level, nobody normally has to approve you, and any address can send a transaction. That does not mean “without restrictions”. User interfaces (websites), infrastructure providers and stablecoin issuers can restrict addresses or regions. For example, according to Decrypt, in March 2022 MetaMask’s default provider (Infura) blocked transactions from Iranian IP addresses. Having a personal wallet does not make you immune to infrastructure-level limits.
2. Transparency. All balances and transactions are visible on-chain. You can see how much a protocol holds, who its largest depositors are and what its contract code says. Transparency does not bring security; it only makes checking possible.
3. Composability. Protocols stack on each other like Lego bricks. A token you receive from a staking protocol becomes collateral in another, and a loan you take goes into a liquidity pool in a third. This composability is DeFi’s strength, and it is also what makes risk chained: if one link breaks, the others are damaged too. Later lessons show this happening in the Kelp DAO case in April 2026 and in the Stream Finance chain in November 2025.
What is TVL, and what does it not tell you?
TVL (Total Value Locked) is the total value of assets locked in the contracts of a protocol or network. Data sites such as DefiLlama add it up, and it is the most common measure of “size” in DeFi. But it has three important limitations:
- It moves with price. If the price of ether halves, the TVL of a protocol holding ether roughly halves too, even if nobody has left.
- Double counting. Because of composability, one asset can be counted in several protocols in a row: once as a staking deposit and once as loan collateral.
- Concentration. A high TVL may belong to a few large wallets. If they leave, liquidity suddenly evaporates.
So a high TVL means “a lot of money is here”, not “it is safe here”. Large protocols have been hacked too.
What replaces the bank, and which risks replace bank risk
In the banking system your main risk is the bank’s failure or restrictions, and in many countries deposit insurance and courts stand behind you. In DeFi the intermediary is removed but the risk is not; it only changes shape:
| Role in a bank | Replacement in DeFi | New risk |
| Bank staff and systems | Smart contract | Code bugs, hacks |
| Bank management | Admin key, multisig or governance (DAO) | Abuse or leak of keys, social engineering |
| Official rate | Oracle (price source) | Wrong or manipulated price |
| Transfers between banks | Bridges between chains | Bridge hacks, unbacked assets |
| Deposit insurance and support | Usually none | Your mistake is not reversible |
According to TRM Labs, from the start of 2026 to mid-September of that year about 1.7 billion dollars was lost across more than 300 hack incidents. That figure is only part of the picture, because phishing scams and malicious signatures are counted separately.
One more risk is specific to the user: full responsibility. If you mistype an address, connect to a fake site or grant unlimited approval to a malicious contract, nobody can reverse the transaction. Many DeFi interfaces and stablecoin issuers also screen addresses against sanctions lists. For users in sanctioned regions, that means a real chance of losing access to an interface or having tokens frozen, which should be weighed seriously before any deposit.
How this course helps
This course is not meant to encourage or discourage you from using DeFi. The aim is that when you meet an “attractive yield” or a new protocol, you can ask: where does this money come from, and where would it break?
If you are not yet comfortable with wallets, seed phrases, networks and fees, take the crypto basics and security courses first. In DeFi, the smallest security mistake can wipe out an entire wallet. Every numerical example in this course is hypothetical and given only to explain a mechanism, not as an investment suggestion.
Common mistakes
- Treating “decentralised” as “safe”; code, admin keys and oracles can each be a point of failure.
- Using a high TVL as a sign of security, without noting that TVL moves with price and may be double counted.
- Assuming a personal wallet means full immunity from restrictions; interfaces, infrastructure and token issuers can limit access.
- Connecting your main wallet to unknown protocols instead of using a separate wallet with a small amount.
- Ignoring chained risk: a token used in three protocols in a row has three points of failure.
What do volume and data say here?
Unlike traditional markets, much DeFi data is public and you can check it yourself:
- Compare TVL with price: if a protocol’s TVL has dropped, see whether asset prices fell or deposits actually left. A fall in the number of tokens matters more than a fall in dollar value.
- Inflow and outflow: fast exits of large deposits from a protocol are often the first sign of concern among informed participants; not a prediction, but a flag for closer inspection.
- Trading volume against TVL: on a decentralised exchange, real trading volume shows whether a pool is actually used or merely filled by token incentives.
- Explorer: open the contract address in the network’s explorer and check whether its code is verified and who the biggest holders are.
None of this is a buy or sell signal; it is a toolkit for assessing risk.
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Frequently asked questions
What is DeFi in simple terms?
A set of financial services such as trading, lending and saving that run through smart contracts on a blockchain instead of through a bank or exchange, usable by anyone with a wallet.
Is DeFi safer than a centralised exchange?
Not necessarily. The risks differ: a centralised exchange has counterparty risk and account freezes, while DeFi has code bugs, admin keys, oracles and your own mistakes. Neither is risk-free.
Does a high TVL mean a protocol is trustworthy?
No. TVL only shows the amount deposited and it moves with price. Protocols with hundreds of millions of dollars in TVL have been hacked.
Education only, not a recommendation to buy or sell; we never give signals. Price examples are illustrative. Test any method on a demo account first, with strict risk management.