Staked Ether (stETH) is a liquidity token representing Ethereum tokens staked to support blockchain operations. It was introduced in 2020 on the Lido protocol, anticipating Ethereum's shift to proof-of-stake. StETH allows trading, borrowing, and liquidity purposes. Staking involves locking cryptocurrency as a validator's stake, incentivizing honest participation. StETH holders participate in transaction validation and receive rewards.