What is Zero-knowledge proof?
Also called: ZK proof, zk-SNARK, zero knowledge
A zero-knowledge proof lets one party prove a statement is true without revealing the underlying data. Verifying the proof is far cheaper than redoing the computation.
In practice
Two uses dominate. Scaling: a rollup proves a batch of transactions was executed correctly, so the base chain verifies one proof instead of every transaction. Privacy: a user proves eligibility, such as being over a threshold, without disclosing the value. ZK engineering is among the scarcest skill sets in Web3.