The goal of decentralized financial technologies aka DeFi is to recreate traditional financial systems (such as lending, borrowing, derivatives and exchanges) using automated tools instead of intermediaries. Fully automated DeFi "building blocks" can be used to create more complex tools. At the moment, Ethereum is the main platform for decentralized finance, but in principle, these ideas can be implemented on any platform for smart contracts - EOS, Tron, etc.