The USD-pegged Dai by the MakerDAO, recently has surpassed the one billion line, first time since its inception. The Ethereum-based protocol mint the new Dai tokens, when you lock your collateral in the smart contract. You get the Dai, and you can use it in the wider Ethereum ecosystem, especially in defi.
The massive growth in the supply also happend after the exploding of defi, in the summer. The Dai is the most decentralized dollar-based stablecoin, so its very popular among traders and yield farmers.