What is DeFi (decentralised finance)?

DeFi, short for decentralised finance, is a set of financial services — lending, borrowing, trading and saving — that run on public blockchains through smart contracts instead of banks or brokers. The idea is that code, not a company, holds the rules, so anyone with a wallet and an internet connection can use the same service on the same terms.

That openness is powerful, but it also removes the safety nets you get from regulated finance. This article explains how decentralised finance actually works and, just as importantly, where it can go wrong.

What is DeFi (decentralised finance)?

DeFi is finance rebuilt as open software. Traditional finance routes your money through intermediaries: a bank holds your deposit, an exchange matches your trade, a broker custodies your assets. In DeFi those functions are written into smart contracts deployed on a blockchain such as Ethereum. When you interact with a DeFi application you are not signing up with a firm; you are sending a transaction to a program that executes automatically and settles on-chain.

Three properties define the category:

• Non-custodial. You keep your assets in your own wallet and grant permission per transaction. There is no account a provider can freeze, but also no one to call if you lose your keys.
• Permissionless. The contracts are open to anyone; there is usually no sign-up, credit check or geographic gate at the protocol level.
• Composable. Applications plug into one another like building blocks, so one protocol’s output can feed straight into another’s input.

Because these properties come as a package, they cannot be separated. The same openness that lets anyone join also means no one is vetting who you interact with; the same self-custody that gives you full control also makes you fully liable for your own mistakes. DeFi does not remove risk so much as move it from institutions onto individuals, and understanding that shift is the foundation for everything else in this guide.

How DeFi works under the hood

Most DeFi activity sits on general-purpose blockchains that can run code. A protocol is a set of audited (ideally) smart contracts that anyone can call. Because the contracts are public, developers can inspect them and other apps can integrate with them without asking permission.

Two mechanisms do most of the heavy lifting. Trading is handled by automated market makers, where a smart contract prices swaps against a pooled reserve of two assets rather than an order book. Lending is handled by pooled money markets, where suppliers deposit assets into a shared pool and borrowers draw against it by posting collateral worth more than they borrow. Interest rates adjust algorithmically with supply and demand, and loans are over-collateralised so the pool can liquidate a position automatically if its collateral falls too far. The depth of these pools is what people mean by on-chain liquidity.

How DeFi differs from traditional finance

The clearest way to understand decentralised finance is to line it up against the system it imitates. The services rhyme, but who holds the assets, who sets the rules and who carries the risk are completely different.

Neither column is simply “better”. Traditional finance trades openness for accountability and safety nets; DeFi trades those protections for openness, transparency and self-custody. Knowing which trade-off you are making is the whole skill.

To see the trade-offs in action, follow a single DeFi loan. Suppose you hold a volatile crypto asset and want stablecoins without selling it. In a DeFi money market you deposit the asset as collateral into a lending contract and borrow stablecoins against it, but only up to a fraction of the collateral’s value. The gap between what you deposit and what you can borrow is the safety buffer. If your collateral falls in price and your loan gets too close to that limit, the contract automatically sells part of your collateral to repay the debt — a liquidation — often with a penalty. No loan officer is involved; the rules were fixed in code before you arrived, they applied the instant your price crossed the threshold, and there is no one to phone for an extension. This is why DeFi loans are almost always over-collateralised: the protocol cannot chase you for repayment, so it protects itself with your collateral instead.

What you can do in DeFi

The common building blocks map loosely onto familiar financial services:

• Trade one token for another through a decentralised exchange.
• Lend and borrow through pooled money markets, always against collateral.
• Provide liquidity to a liquidity pool and earn a share of trading fees — the mechanic behind yield farming.
• Hold stablecoins as an on-chain unit of account.
• Take part in governance using a governance token that lets holders vote on protocol changes.

The size of this activity is often summarised by Total Value Locked, an estimate of the assets deposited in DeFi contracts.

The risks you must understand

DeFi removes intermediaries, and with them the protections those intermediaries are required to provide. The risks are real and specific:

• Smart-contract risk. If the code has a bug or is exploited, funds can be drained irreversibly. An audit reduces this risk but never eliminates it.
• No deposit protection. There is no equivalent of bank deposit insurance. If a protocol fails or is hacked, there is usually no scheme to make you whole.
• Impermanent loss. Supplying assets to a pool can leave you worse off than simply holding them when prices move apart — explained in our guide to impermanent loss.
• Rug pulls and scams. Anyone can deploy a token or a fake app. Malicious teams can drain liquidity or ship contracts designed to trap funds.
• Liquidation risk. Collateralised loans can be closed out automatically and at a loss during sharp price moves.
• Key and approval risk. Lose your seed phrase and your funds are gone; grant a malicious contract a token approval and it may move your tokens.

None of this is a reason for panic, but it is a reason for caution. Understanding the mechanism is the point of learning about DeFi in the first place.

DeFi, tax and regulation

Being on-chain does not put activity outside the law. Many tax authorities treat crypto disposals, swaps and rewards as taxable events, and regulators are steadily extending rules to cover parts of the sector. How a given activity is taxed or regulated depends heavily on where you live, and the rules are changing quickly.

This article is educational and is not financial, legal or tax advice. Rules differ by jurisdiction; before you act, check the position in your own country and consider speaking to a qualified professional. Never commit money you cannot afford to lose to a system with no safety net.

The bottom line

DeFi is an attempt to rebuild financial services as open, non-custodial software running on public blockchains. It offers genuine openness and composability, and it removes gatekeepers — but it also removes the intermediaries who normally absorb risk, so responsibility shifts almost entirely onto the user. The most common mistakes are chasing headline returns without understanding smart-contract and impermanent-loss risk, trusting anonymous projects, and assuming “decentralised” means “safe”. Learn the mechanics first; the whole point of decentralised finance is that no one else is checking your work.