Glossary
ZK-STARK
A succinct zero-knowledge proof that requires no trusted setup and is post-quantum secure, at the cost of larger proof sizes than SNARKs.
STARK = Scalable Transparent ARgument of Knowledge. They use hash-based cryptography instead of pairings, which makes them transparent (no trusted setup), resistant to quantum attack, and faster to prove for large computations.
The trade-off is proof size — STARKs are larger than SNARKs, so on-L1 verification costs more. StarkNet uses STARKs; zkSync and Scroll use SNARK-based proof systems. Some stacks now combine both: STARK for the heavy proving, SNARK to compress the result for L1.