Glossary
Zero-Knowledge Proof
A cryptographic proof that lets one party convince another that a statement is true without revealing why — used for privacy and for compressing computation.
A zero-knowledge proof discloses only the fact "I know x" without disclosing x itself. The classic toy example: proving you know the combination to a safe without opening the safe.
In blockchains, ZK proofs are used two ways. For privacy: prove you have funds, or that a transaction is valid, without revealing the amount or the addresses (Zcash, Tornado Cash). For scaling: prove a batch of transactions was processed correctly, so the chain only verifies the proof rather than re-executing every transaction (ZK rollups).