How Do Zero-Knowledge Proofs (ZKPs) Ensure Transaction Validity without Revealing Underlying Data?

ZKPs use complex cryptography to allow a "prover" to convince a "verifier" that a statement is true without revealing any information beyond the statement's validity. In ZK-Rollups, the statement is "this batch of transactions is valid." The proof itself is a small, verifiable cryptographic artifact that attests to the correct state transition, keeping the individual transaction details private.