DeFi (decentralized finance) uses smart contracts to offer lending, trading, derivatives, and yield without a classic bank desk in the middle. Users keep custody in wallets and interact with protocols on-chain. The promise is open access and composable money tools. The cost is code risk, oracle risk, governance risk, and user-error risk that no call center can reverse once a bad signature is confirmed.
Why it matters
DeFi is where on-chain liquidity, stablecoin settlement, and incentive programs meet. Traders watch total value locked, utilization, funding analogs, and exploit headlines because those prints move tokens and risk appetite. A rising TVL line is not the same as safety. It is capital parked in contracts with explicit assumptions about collateral, oracles, and who can pause or upgrade the system.
Self-custody cuts intermediary delay and also removes many safety nets. Approving the wrong spender, signing a phishing payload, or ignoring an unaudited fork can wipe a wallet fast. Calm habit is to verify URLs, limit approvals, start small, and read what collateral and oracle a pool actually uses before size grows.
Not every yield is free alpha. Emissions, temporary incentives, and leveraged loops can inflate returns until they stop. Desk framing asks who pays the yield, what fails in a stress path, and whether exit liquidity will still be there when many users leave together. If those answers are vague, the APY is a marketing number, not a plan.
Example
You deposit collateral into a lending pool and borrow a stablecoin against it. Rates, liquidation rules, and oracle updates now matter as much as the token thesis. If the contract is exploited or the oracle misprices collateral, the position can fail even while the broader market looks calm. That is why DeFi size starts small and grows only after the exit path is tested.