Tether provides a secure, fast, and low-cost way to store, send, and receive money on the Blockchain as if it were bitcoin.
Tether (USDT) is basically a crypto currency of its own and one tether or one token represents one US dollar in value and that's pegged to the reserves the tether company have in their bank accounts. That's why Tether is called a stablecoin because it is claimed to always be worth $1.00, though sometimes fluctuates a bit.
Tether coin uses blockchain via the Omni Layer protocol. The Omni Layer protocol is the software with an open source code that interacts with blockchain, ensuring the release and redemption of crypto currency token on the basis of Bitcoin.