A cryptographic protocol that allows a party to prove possession of information, such as a private key, without revealing it. Zero-knowledge proofs offer "proofs of validity" to convey information from a prover to a verifier. They are used to verify transactions on a blockchain very quickly.
Layer 2 Blockchain - SNARK and STARK
Zk-SNARK and zk-STARK are examples of proof
methods used in Layer 2 blockchain rollups. Zk-SNARK (zero-knowledge succinct non-interactive argument of knowledge) hides addresses and transacton amounts but allows the network to verify and confirm a transaction. Zk-SNARK is used by privacy-oriented Zcash to provide anonymous payments (see Zcash
Zk-STARK (zero-knowledge succinct transparent argument of knowledge) offers more scalability and transparency and is touted as the efficient successor to zk-SNARK. See Layer 2 blockchain