Slashing is a penalty system used in Proof of Stake (PoS) blockchain protocols to economically punish a node or a group of nodes that deviate from the protocol's specified actions. It works by taking away some or all of the validator's stake, which was previously committed as collateral. Slashing is used primarily for safety violations, which are more serious than liveness violations because they can result in the loss of user funds. This mechanism is unique to PoS systems and provides a way for the blockchain to enforce penalties against nodes that do not behave according to the protocol.