Tether (USDT) is a stablecoin (stable cryptocurrency) pegged to fiat currency, namely the US dollar. It was issued by Tether Limited and is designed to provide price stability and liquidity in the cryptocurrency market. Each USDT token is backed by a 1:1 reserve ratio with its corresponding fiat currency, making it one of the most reliable and predictable assets in the cryptocurrency world.

The primary purpose of Tether is to provide stability in the face of volatility in the cryptocurrency market. It allows traders and investors to quickly and securely convert their assets into the stable digital equivalent of the US dollar without the need to use traditional banking systems.

However, Tether has also come under fire due to questions about the transparency of its reserves and reliability. There has been a long history of mistrust in Tether Limited, which has not always provided audit reports on the state of its reserves. This raises concerns that there may not be enough fiat funds to cover all USDT tokens issued.

Despite this, Tether remains one of the most popular and widely used stablecoins in the world due to its widespread support on major cryptocurrency exchanges and ease of use for trading and storing digital assets.