Liquid is one of Bitcoin's first sidechain implementations. A sidechain is a blockchain that runs parallel to the main blockchain. Sidechains enable the use of a token from the main chain, in this case, bitcoin, to be used on a separate chain, the Liquid sidechain. Advantages of using a sidechain include increased functionality and speed.
With the release of Liquid, Blockstream announced that it has partnered with 23 bitcoin companies, including exchanges, brokers, and custodians to help manage the sidechain. These companies will use Liquid to convert bitcoin into LBTC — which will be pegged to an actual bitcoin. Using LBTC companies can transfer value more quickly than on the main Bitcoin blockchain. Companies can also instantly convert their LBTC back to bitcoin when necessary. (Source: CoinDesk)