Zcash is a cryptocurrency aimed at using cryptography to provide enhanced privacy for its users compared to other cryptocurrencies such as Bitcoin.
Like Bitcoin, Zcash has a fixed total supply of 21 million units
Transactions can be “transparent” and similar to bitcoin transactions in which case they are controlled by a t-addr, or can be a type of zero-knowledge proof called zk-SNARKs; the transactions are then said to be “shielded” and are controlled by a z-addr. Zcash coins are either in a transparent pool or a shielded pool; as of December 2017 only around 4% of Zcash coins were in the shielded pool and at that time most wallet programs did not support z-addrs and no web-based wallets supported them.
Zcash affords private transactors the option of “selective disclosure”, allowing a user to prove payment for auditing purposes. One such reason is to allow private transactors the choice to comply with anti-money laundering or tax regulations. “Transactions are auditable but disclosure is under the participant’s control.” The company has hosted virtual meetings with law enforcement agencies around the U.S. to explain these fundamentals and has gone on the record of saying that “they did not develop the currency to facilitate illegal activity”.