Decentralized Finance (or simply DeFi) refers to an ecosystem of financial applications that are built on top of blockchain networks.
More specifically, the term Decentralized Finance may refer to a movement that aims to create an open-source, permissionless, and transparent financial service ecosystem that is available to everyone and operates without any central authority. The users would maintain full control over their assets and interact with this ecosystem through peer-to-peer (P2P), decentralized applications (dapps).
The core benefit of DeFi is easy access to financial services, especially for those who are isolated from the current financial system. Another potential advantage of DeFi is the modular framework it is built upon - interoperable DeFi applications on public blockchains will potentially create entirely new financial markets, products, and services.