Tether, sometimes known as USDT, is one of the first stable currencies. Every Tether token (USDT) is required to be pegged to one US dollar, providing traders with a secure storage option when they depart BTC, ETH, or other matching virtual currencies. Tether's currencies are "produced" and then sold to investors, much like a banking system. In theory, someone who possesses a large quantity of Tether can send it to Tether Limited and get paid in cash. Tethers are based on blockchains and use the Omni Protocol, which was created specifically for Tether Limited.
The USDT, on the other hand, has sparked a lot of controversy. Its reserve has been the subject of several debates.