Zcash is a privacy-focused blockchain and cryptocurrency that was developed in response to Bitcoin's flaws. It uses the same algorithm as Bitcoin but improves upon it by enabling semi-transparent processing. In simple words, this means that it eschews the radical transparency of Bitcoin's blockchain for a more nuanced implementation. In this implementation, user transaction data is revealed selectively.
Another important property of Zcash is the fungibility of its tokens. This means that all parties within a transacting system treat Zcash tokens as equal, irrespective of transaction history. In public blockchains, these properties are impossible because it may be possible to blacklist tokens from a certain party based on its transaction history. In this respect, Zcash resembles present-day cash. It is difficult to discriminate against paper dollars from specific properties because their transaction history is difficult to glean.