xDAI was the legacy name of a layer-1 chain—Ethereum-compatible and high-performance, which is now formally named Gnosis Chain. It became the first in history to use a stablecoin as its gas token (which means predictable transaction costs rather than volatile market-driven rates)
Originally based on the AuRa (Authority Round) model and then moving to a Proof-of-Stake, xDAI provides instant finality & has very cheap transaction fees, usually less than a cent. It has full EVM compatibility, which means that developers can deploy smart contracts and DApps with little friction.
Its ecosystem depends on Dai being locked up by the xDAI Bridge to mint xDAI in the sidechain. The network has since rebranded to Gnosis Chain in order to better fit with the surrounding Gnosis ecosystem. xDAI will always remain a key part of crypto history as one of the earliest successful scalability solutions for decentralized finance (DeFi).