How many types of USDT are there?

I'm quite curious about the various forms of USDT. Could you please enlighten me on how many different types of USDT exist? I've heard rumors of several variations, but I'm not entirely sure which ones are legitimate and which ones might be fraudulent. Understanding the different types would help me navigate the cryptocurrency market more confidently. Could you break down the various types for me, perhaps explaining their unique features and uses? Thank you in advance for your assistance in clarifying this matter.