What is Staking?
Staking locks tokens to help secure a proof-of-stake network in return for rewards. The stake is collateral, so it can be reduced if the validator behaves badly.
In practice
Rewards are compensation for real risk: slashing, lock-up periods, and validator downtime. Liquid staking issues a tradable receipt so the position stays usable in DeFi, at the cost of an extra contract in the trust chain and, at scale, concentration in a few providers.