DeFi Staking, refers to the practice of locking crypto assets into a smart contract in exchange for becoming a validator in a DeFi protocol or a Layer 1 blockchain and earning rewards for performing the duties the role requires.
Yield Farming (a type of DeFi staking), is a means of earning interest on your cryptocurrency, similar to how you'd earn interest on any money in your savings account. And similarly to depositing money in a bank, yield farming involves locking up your cryptocurrency, called "staking," for a period of time in exchange for interest or other rewards, such as more cryptocurrency.