Tether is the most-used stablecoin, a cryptocurrency designed to hold a steady value of one US dollar per token. Its ticker is USDT. Tether Limited, the company behind it, issues the token and says each one is backed by its reserves, so the price tracks the dollar rather than swinging the way Bitcoin or other crypto assets do. The first tokens were issued on October 6, 2014, originally on the Bitcoin blockchain. Today USDT runs on many separate networks, including Ethereum, Tron, Solana, Avalanche, and Polygon, which means the same dollar-pegged token can move across several chains.
The point of a stablecoin is to give traders and apps a dollar they can hold and send on a blockchain without leaving the crypto system. Most people who buy and sell crypto use USDT as the cash leg of a trade: they price coins against it, park value in it between trades, and move it between exchanges in minutes at any hour. That role made it the backbone of crypto liquidity. In 2019 it passed Bitcoin to become the most traded cryptocurrency by volume, and it has held the largest share of the stablecoin market since.
The peg holds through backing and redemption rather than any algorithm. Tether Limited states that every token is matched one-to-one with a fiat currency and backed fully by its reserves, so a holder can in principle redeem USDT for dollars and arbitrage keeps the market price near a dollar. The reserves are not a single pile of cash; they include US Treasury bills along with other assets such as precious metals, Bitcoin, secured loans, and other investments. The exact make-up shifts over time and is reported by the company in periodic attestations. Because those holdings are not all cash, the quality and transparency of the backing have drawn regulatory attention and debate over the years, and that is part of why some users prefer a different stablecoin.
Tether Limited is a subsidiary of Tether Holdings Limited, based in the British Virgin Islands. For a reader, USDT is a tool for holding and moving dollars on a blockchain, useful for trading and transfers, but it is a claim on a private company's reserves rather than an actual bank dollar. The peg buys you price stability against the dollar. It does not buy you the protection of a bank deposit.