Is USDT backed by USD?

I've often heard that USDT is somehow connected to the US dollar, but I'm not entirely sure how. Could you clarify for me? Is USDT actually backed by USD in a direct way? I'm trying to wrap my head around the concept of stablecoins and how they maintain their pegged value. If USDT is indeed backed by the US dollar, how does that process work? And what happens if the value of the US dollar fluctuates? Would that affect the value of USDT? I'm really curious about this and would appreciate a detailed explanation.