Glossary
Proof of Stake (PoS)
A consensus mechanism in which validators are chosen to propose and attest to blocks in proportion to the amount of native token they have locked as stake.
In a proof-of-stake system, validators lock up the chain's native token. The protocol picks them to propose and attest blocks roughly in proportion to their stake; honest behavior earns rewards, and provably bad behavior — double-signing, downtime — is punished by "slashing" part of the stake.
PoS replaces the energy cost of PoW with an economic cost: attacking the chain requires acquiring and then sacrificing a controlling share of the staked token. Ethereum switched from PoW to PoS in the 2022 Merge.