Zk-SNARK (Zero-Knowledge Succinct Non-Interactive Argument of Knowledge) is most closely related to zero-knowledge proofs. Zero-knowledge proofs are cryptographic methods that allow one party to prove to another that they know a value without revealing the value itself. Zk-SNARKs are a specific implementation of zero-knowledge proofs that are characterized by their succinctness (the proofs are very short) and non-interactivity (the proof generation does not require back-and-forth communication). They are widely used in blockchain technology, particularly in privacy-focused cryptocurrencies like Zcash.