How much is $1 Dollar?

Excuse me, could you please clarify something for me? I'm a bit confused about the value of the US dollar. Specifically, I'm wondering how much exactly is $1 Dollar? I understand that it's the basic unit of currency in the United States, but I'm looking for a more detailed explanation of its worth or value in the global financial system. Is there a fixed amount that it's equal to, or does it fluctuate based on various factors? I'd appreciate any insight you can provide on this matter. Thank you.