What is the USDT?

Excuse me, I'm a bit new to the world of cryptocurrencies. Could you possibly explain what USDT is? I've heard it mentioned a few times, but I'm not entirely sure what it stands for or how it works. Is it a type of digital currency? And if so, how is it different from other cryptocurrencies like Bitcoin or Ethereum? I'm quite interested in learning more about this topic, so any information you could provide would be greatly appreciated.