Plain meaning
Start with the shortest useful explanation before going deeper.
Financial services built on blockchain smart contracts that operate without traditional intermediaries (banks, brokers). DeFi includes lending, borrowing, trading, insurance, and derivatives. Key properties: permissionless (anyone can participate), composable (protocols can be combined), transparent (open-source, auditable). Solana DeFi TVL has exceeded $5B, led by Jupiter, Raydium, Marinade, and Kamino.