Mina aspires to be the world’s tiniest blockchain, with claims that its protocol maintains a constant size of around 22 KBs. This is ostensibly achieved by using recursive zk-SNARKs — the same technology that is used by the privacy-centric cryptocurrency, Zcash (ZEC). However, whereas the latter utilizes this technology to provide greater privacy to its users, the former employs it for scalability.
A zk-SNARK, which stands for zero-knowledge succinct non-interactive argument of knowledge, allows a party to prove that they have possession of certain information without revealing what that information is. It is similar to how a smartphone can recognize its owner without storing the person's actual identity data.