Zk-SNARKs is an abbreviation for Zero-Knowledge Succinct Non-Interactive Argument of Knowledge. Considered to be a novel form of Zero-Knowledge cryptography, Zk-SNARKs is proof construction that a participant can verify information; it is synonymous to a secret key. This is done both without revealing information itself or asking for interaction between prover and verifier.
Zcash is seen as the first widespread application of Zk-SNARKs. Zcash’s strong privacy guarantee is taken from the fact that transactions shielded in the currency may be fully encrypted on the blockchain, with it still being able to be verified through the network’s consensus rules through the use of Zk-SNARK proofs.