Think of DeFi has an escape solution from your traditional centralized banking system. It's an ecosystem built on Ethereum blockchain, it has integrated protocols and decentralized financial tools with huge uses cases targeted to be used by almost anybody, be it individuals or developers. With this technology, you are able to build defi protocols into several institution like banking, exchanges, gaming platforms, insurance and even tokenization.
What i love most about it is the lending & borrowing, permissionless, staking, stablecoins, protection of identity (which was becoming a problem with crypto space)