What is DeFi? How decentralized finance works

Decentralized finance, usually called DeFi, is software that lets you use financial services through blockchain-based smart contracts. A wallet signs the instructions, and the contract applies its published rules for a swap, loan, deposit, or withdrawal. The signed action is recorded on the network.

That changes who controls the transaction, yet it does not make every transaction safe or suitable. Before you approve a DeFi transaction, you need to understand what the contract can do, what asset you can lose, and which price or liquidity condition can change the outcome.

What decentralized finance means

DeFi is a group of applications that use smart contracts to deliver financial functions on a blockchain. Ethereum describes smart contracts as the programs that provide these services without a conventional intermediary managing each instruction.

A smart contract is code deployed to a blockchain. It can hold assets and apply rules after your wallet signs a transaction, so the transaction history and contract logic are available for inspection on the network. Public code still needs careful evaluation.

The word decentralized describes the operating model, not a promise that no person or company influences a protocol. Protocol teams can publish upgrades, governance groups can vote on parameters, and an interface can block access even when the underlying contract remains on-chain.

How a DeFi transaction works

A DeFi transaction usually has four parts: your wallet, an application interface, a smart contract, and the blockchain network that records the signed request. The interface helps you prepare the transaction, while the wallet is where you review and sign it.

Your wallet signs an instruction

When you connect a wallet, the site can ask to view your public address or request a signature. A signature can confirm a message, authorize a token allowance, or submit a transaction that changes blockchain state, and those actions have different consequences. Your wallet should identify the request type before you sign.

An allowance gives a contract permission to spend a specified token from your wallet. Read the token, contract address, amount, and network before approving it because an allowance can persist beyond the swap or deposit you intended to make.

The smart contract applies its rules

After you submit a transaction, network validators include it in a block and the contract executes its code. If the call meets the contract’s conditions and you have enough funds for the transaction, the contract updates balances or records your position. Network fees are part of that submitted transaction.

Blockchain execution does not mean a human support team can reverse a mistake. Sending assets to a wrong address, signing a malicious approval, or entering a contract with a defect may leave no practical recovery path.

What people do in DeFi

DeFi applications cover several financial activities, but each uses a different contract design and risk model. Start by separating the activity you want from the protocol mechanism that performs it.

Swap tokens

A decentralized exchange, or DEX, lets you exchange one token for another through a contract. Many DEXs use liquidity pools rather than a traditional order book, with pool reserves determining the quoted exchange rate. The pool mechanism creates price impact for larger trades.

Uniswap documentation describes a pool as a contract holding reserves of two ERC-20 tokens. Your trade changes those reserves, which is why a larger trade can receive a worse price than the number shown before you submit it.

Lend or borrow assets

Lending protocols accept deposits that other users can borrow under collateral rules. A borrower locks one asset, borrows another, and must maintain enough collateral value as prices move. The collateral rules are protocol-specific.

Aave uses a health factor to measure the safety of a borrowing position. If that value falls below 1, the position can become eligible for liquidation, which means the protocol can sell collateral to repay the debt.

Provide liquidity

Liquidity providers deposit tokens into a pool so swaps can happen without matching a buyer to a seller. In return, they may receive a share of pool fees, subject to the protocol’s rules. The pool composition changes as traders use it.

Fee income is only one side of the position. If the relative price of the deposited assets moves, the pool can rebalance your holdings, and the result may differ from holding the same assets outside the pool.

What changes when you use DeFi

DeFi gives you direct control over a wallet and the ability to interact with public contracts from many places. It also gives you direct responsibility for private keys, transaction approvals, network fees, and contract selection.

Question	DeFi answer	Why it matters
Who authorizes the action?	Your wallet signature	A signed transaction can be hard to undo.
Who applies the rules?	The smart contract	Read the protocol documentation and contract details.
What sets a swap price?	Pool reserves and protocol rules	Price impact and slippage can change what you receive.
What protects a loan?	Collateral and liquidation parameters	A price drop can trigger liquidation.

Risks to check before you approve anything

A low transaction fee or polished interface does not evaluate the protocol for you. The first check is always the action your wallet is asking you to authorize.

Smart contract and protocol risk

Contracts can contain bugs, flawed economic rules, upgrade permissions, or dependencies that fail. An audit can provide evidence that someone reviewed code, but it does not guarantee the protocol will perform safely under every market condition.

Price, liquidity, and liquidation risk

Token prices can move faster than you expect, and a thin pool can make a trade much more expensive than the initial quote. Borrowing adds liquidation risk because the value of collateral and debt can move in opposite directions.

For a borrowing position, record the collateral asset, borrowed asset, loan-to-value limit, liquidation threshold, and health factor. Those parameters matter more than an advertised borrowing rate when prices are volatile.

Wallet approvals and custody

Self-custody means you control the wallet keys, and it also means you are responsible for protecting them. Never share a seed phrase or private key, and verify that a site uses the contract address and network you intended to use.

Consumer regulators such as the DC Department of Insurance, Securities and Banking warn that DeFi can involve fraud, loss of funds, and limited consumer protections. Treat that warning as part of the product design, not a footnote.

A useful first pass before using a protocol

Use a small amount only after you can explain the contract action in plain language. Check the protocol documentation, the official contract address, the token approval amount, the network, the transaction simulation if your wallet provides one, and the withdrawal or liquidation conditions.

DeFi is useful when you understand the transaction you are signing and can accept the protocol-specific risk. Read the Ethereum DeFi overview, Uniswap’s explanation of pools and swaps, and Aave’s liquidation guidance before moving assets.

Frequently asked questions

These answers cover the boundary between a DeFi transaction and the risks that remain with the person signing it.