USD Tether is a Bitfinex issued ERC-20 token which is claimed to be backed by dollar at 1:1 ratio. There are controversial opinions about this and some say it's a scam.
Do you trust USDT or believe it might be a scam?
I think that in the current market situation and against the background of all other stable coins Tether is the best one that exists so far. I don't think it's a scam, despite rumors that Tether lied about the liquidity of the coins they put on the market.