Do I need TRX to send USDT?

I'm a bit confused about cryptocurrency transactions, and I'm trying to figure out if I need TRX to send USDT. Could you clarify for me? I've heard that TRX is a token used on the Tron blockchain, but I'm not sure if it's a requirement for sending USDT. Is USDT a Tron-based token, or can it be sent independently? If TRX is indeed necessary, why is that? And if not, what's the best way to send USDT? I'm still learning about this whole crypto ecosystem, so any explanation you can provide would be greatly appreciated.