Quoting:
Liquid is a sidechain-based, inter-exchange settlement network linking together cryptocurrency exchanges and institutions around the world, enabling faster Bitcoin transactions and the issuance of digital assets.This protocol developed by Blockstream is a competitor to Lightning network, but operates under a fully different principle. While Lightning works under a principle of a bilateral contract being done by two or more parties and changing terms of the resulting contract with each transaction, Liquid uses a sidechain which backs BTC into a new currency called L-BTC which processes transactions much faster (due to higher block frequency) and with greater confidentiality by hiding amounts of crypto being transferred from wallet to wallet.
Due to the nature of Liquid Network being developed by a private company and is not accounted under any BIP proposal, the standard enjoys only limited support outside of Blockstream’s own line of products and devices.