Glossary
Groth16
A SNARK proof system (Jens Groth, 2016) with the smallest known proof size — three group elements — but requiring a per-circuit trusted setup.
Groth16 produces proofs of just three elliptic-curve elements (~192 bytes on BLS12-381), with verification costing three pairings. The proofs are smaller than any other production SNARK system, which is why Zcash, Tornado Cash, Semaphore, and many voting protocols use it.
The trade-off is the trusted setup: parameters must be generated per circuit via a multi-party ceremony, and if all participants collude the proofs can be forged. Modern alternatives (PLONK, HyperPLONK, Groth-Sahai) reduce the setup to a universal one-time ceremony or eliminate it entirely.