Threshold USD, or thUSD, is a decentralized stablecoin pegged 1:1 against the USD price.
To borrow thUSD, you provide tBTC (v2) as collateral. This allows Bitcoin holders to bridge their BTC via tBTC and borrow against their Bitcoin holdings. The borrowed thUSD can then be deployed in the larger DeFi ecosystem. For example, you could deposit it to an exchange or lending market to earn yield, swap it into other stablecoins such as USDC etc.
Each thUSD is fully backed by tBTC with a minimum 110% collateral ratio. The low collateral ratio is made possible due to the underlying "stability pool" - a pool of thUSD that will automatically purchase liquidations basically the moment they occour. This enables lower liquidation ratio than auctions would (because auctions are slow and affected by price fluctuations).
Threshold USD is a fork of Liquity Protocol. However, thUSD differs in a few ways. Firstly, there is no LQTY token in thUSD. Whenever minting of thUSD or redemptions occurs, a fee is taken and the profits accrue directly to the PCV (Protocol Controlled Value) which again is owned by the Threshold DAO.
As T holders are the ultimate beneficiaries of Threshold DAO, they stand to gain monetary value from usage of the Threshold USD Protocol.