zkSync is a layer-2 scaling solution for Ethereum, which aims to increase transaction throughput while reducing transaction fees and confirmation times. It is built on top of the Ethereum blockchain, but uses zero-knowledge proofs to batch and compress transactions before they are settled on the main chain.

The technology behind zkSync is called zkRollup, which uses zero-knowledge proofs to verify the correctness of a batch of transactions without requiring each individual transaction to be processed on the main Ethereum network. This means that transactions can be processed more quickly and cheaply, while still maintaining the security and trustlessness of the Ethereum blockchain.

zkSync also offers instant withdrawals, allowing users to transfer funds from the zkSync network back to the Ethereum mainnet instantly, without having to wait for the usual confirmation times.

The zkSync protocol is open-source and has been audited by multiple security firms to ensure its safety and reliability. It is being developed by Matter Labs, a team of blockchain developers and researchers focused on improving the scalability and security of blockchain networks.