Plain meaning
Start with the shortest useful explanation before going deeper.
A decentralized lending and borrowing protocol on Solana that enables users to supply assets to earn yield or borrow against collateral. marginfi features a risk engine that evaluates asset correlations and concentration risk, isolated lending pools for higher-risk assets, and integration with Solana DeFi composability. It became one of the largest lending protocols on Solana by TVL during 2023-2024.