Tether (USDT) is a type of cryptocurrency known as a stablecoin. It was launched in 2014 by a company called Tether Limited. The main purpose of Tether is to provide stability in the volatile cryptocurrency market by pegging its value to a traditional fiat currency, usually the US dollar (USD). This means that each Tether token is supposed to represent one US dollar.

Tether achieves this stability through a mechanism known as fiat collateralization. Tether Limited claims that for every USDT token in circulation, they hold an equivalent amount of USD in reserve. However, the company's claims have been a subject of controversy and scrutiny, and there have been concerns about the transparency and verifiability of their reserves.

Initially launched on the Bitcoin blockchain using the Omni Layer protocol, Tether has expanded to other blockchains, including Ethereum and Tron, using different technical standards such as ERC-20 and TRC-20.

Tether has gained significant popularity and is widely used in the cryptocurrency industry. It is used by traders and exchanges as a stable store of value, as well as for arbitrage and liquidity purposes. Many cryptocurrency exchanges also offer trading pairs with USDT as a base currency, allowing users to trade various cryptocurrencies against the value of Tether.

It's important to note that while Tether is designed to maintain a 1:1 peg with the US dollar, its value can fluctuate slightly due to market dynamics and supply-demand factors. Additionally, the use of Tether carries some risks, including regulatory uncertainties, counterparty risks, and concerns about the veracity of Tether Limited's reserve claims. As with any cryptocurrency or financial instrument, it's advisable to do thorough research and exercise caution before engaging with Tether or any other stablecoin.