What is Proof of Stake (PoS)?
Answer
Proof of Stake (PoS) is a consensus mechanism where validators are chosen to create new blocks based on the amount of cryptocurrency they stake (lock up as collateral) rather than computational work. How it works in Ethereum: (1) Staking — validators deposit 32 ETH as collateral; (2) Attestation — validators are randomly selected to propose and attest to blocks each epoch (~6.4 minutes); (3) Rewards — validators earn staking rewards (~3-5% APY) for honest participation; (4) Slashing — validators behaving maliciously (double voting, equivocation) have a portion of their stake destroyed. PoS advantages over PoW: (1) Energy efficiency — ~99.95% less energy than PoW; (2) Lower entry barrier — no specialized hardware required; (3) Economic security — attacking requires owning 1/3+ of staked ETH (economically self-destructive). Disadvantages: richer validators have more influence ("rich get richer"); newer and less battle-tested than PoW.