DeFi as it is popularly known, refers to a niche within the cryptocurrency space comprising applications facilitated decentralized financial services.
As opposed to traditional financial services offered by banks, brokers and relevant institutions, the cryptocurrency space relies on decentralized applications to provide similar services, including market-making, trading, lending, borrowing, fixed loans, passive income generation, asset swaps, derivatives and more.
This entire subset in the cryptocurrency space is known as decentralized finance or DeFi, since the operation of its component services relies on distributed networks and participants.