Tether is a token issued by Tether Limited and part of the Bitfinex trading platform. It was built using Omni Layer digital currency protocol that works on the Bitcoin blockchain.
This token's main purpose is to stabilize traders and members of the cryptocurrency market. Tether is said to be backed US dollars on Tether Ltd bank account accounts. Tether's price is therefore not as volatile than other cryptocurrencies. This is not yet proven, and it is why the U.S. Commodity Futures Trading Commission subpoenaed Bitfinex and Tether. Tether Ltd also stated that Tether tokens are not financial instruments and owners of Tethers do not have any legal rights or guarantees for losses.
Tether, however, is a popular token that is used by many exchanges (mostly crypto to crypto-only ones) as their main stablecoin. The value of Tethers increased to $2.8 billion. Tethers accounted for around 80% of Bitcoin volume during summer 2018.