Have you ever thought of banks but decentralized??

That's DeFi for you!

DeFi stands for decentralized finance.

It is a system of financial applications built on blockchains (mainly Ethereum and others) that operate without traditional banks or intermediaries. 
Instead of going through a bank or broker, you use smart contracts — code that runs automatically — to borrow, lend, trade, invest, or earn interest.

You can lend your spot ETH on different websites and get a loan to use It for other matters. But be careful! U may get liquidated if the price drops.