A: A zero-knowledge proof is a cryptographic method that allows one party (the prover) to prove to another party (the verifier) that they know a specific piece of information, without revealing the actual information itself. Think of it as proving you know the password to a vault without ever saying what the password is. In blockchain applications, ZK proofs enable privacy-preserving transactions, scalable computations, and regulatory compliance. For example, you could prove you're over 18 without showing your birthdate, or prove you have sufficient funds for a transaction without revealing your account balance. The technology maintains three key properties: completeness (valid proofs are always accepted), soundness (invalid proofs are always rejected), and zero-knowledge (no information beyond the validity of the statement is revealed).