Tether (USDT) is the largest and most widely used stablecoin, a type of cryptocurrency designed to maintain a stable value by pegging it to an external asset, specifically the U.S. dollar at a 1:1 ratio. Tether aims to offer a digital dollar that can be transacted on blockchains without the volatility typically associated with other cryptocurrencies like Bitcoin or Ethereum. 

Tether is a vital part of the cryptocurrency ecosystem, offering a bridge between traditional fiat currency and the digital asset space. Its stability and liquidity make it a valuable tool for traders and businesses, but it remains a controversial entity due to persistent concerns over transparency, reserve adequacy, and regulatory complianc.