Is Usdt an ERC token?

Could you please clarify for me if USDT is indeed an ERC token? I've been hearing a lot about it in the crypto community but I'm still not entirely sure about its technical details. Is it based on the Ethereum blockchain? And if so, what does that mean for its functionality and interoperability within the crypto ecosystem? I'd appreciate it if you could break it down for me in a way that's easy to understand. Thank you!