Plain English
A flash loan is a loan that must be borrowed and repaid in the same blockchain transaction. No collateral required. If you cannot repay within the transaction, the entire transaction reverts as if nothing happened.
How it actually works
Flash loans are possible because of how blockchains work: a transaction is atomic. Either every step succeeds or none do. Aave, dYdX, and others offer flash-loan facilities. Sophisticated users (or bots) borrow huge amounts, perform multiple operations — arbitrage, collateral swaps, liquidations — and repay the loan all in one transaction. If anything fails, the transaction is rolled back and no loan was ever taken.
What it means for you
For most members, flash loans are not a personal tool — they are an artifact of how DeFi protocols compose. The relevant fact: flash loans are how many protocol exploits are executed. Any DeFi position you hold is potentially exposed to flash-loan-driven manipulation of its dependencies.
We cover flash loans as part of DeFi risk analysis. The question is not whether to take one yourself, but whether the protocols you use are robust against flash-loan attacks.
Educational content only. Not investment, tax, or legal advice.