What Is DeFi? — DeFi Dojo

The short version

DeFi, short for decentralized finance, is a set of financial applications — lending, trading, saving, borrowing — built on public blockchains instead of run by banks or brokerages. The rules live in code that anyone can read, and anyone with a wallet can use the app directly, without opening an account or asking permission.

Decentralized vs. traditional finance

In traditional finance, a bank sits in the middle of every transaction: it holds your money, approves your loan, and can freeze your account. In DeFi, that middle layer is replaced by a smart contract — code deployed on a blockchain that holds funds and enforces rules automatically. No single company owns it, and it runs the same way for everyone who interacts with it.

What you can actually do in DeFi

Lend and borrow — deposit assets to earn interest, or post collateral to borrow against it.
Trade — swap one token for another through automated market makers instead of a traditional order book.
Provide liquidity — deposit assets into a pool that others trade against, earning a share of fees.
Stake — lock up assets to help secure a network or protocol in exchange for rewards.

Key idea Your wallet is your login. There's no separate username or password — the private key controlling your wallet is what proves an action came from you.

Why it matters

DeFi apps are composable — one protocol's output (like a deposit receipt token) can be plugged directly into another protocol. That's what people mean by "money legos": DeFi primitives snap together into more complex financial products, all without a central gatekeeper approving the combination.