What are the 51 states?

Excuse me, but could you clarify something for me? When you mention "the 51 states," I'm a bit confused. I'm aware that the United States of America is composed of 50 states, but where does this notion of a 51st state come from? Are you referring to a potential future state, perhaps one that's been proposed or is in the process of becoming a state? Or is there some misunderstanding or cultural reference I'm not aware of? It would be greatly appreciated if you could elaborate on your question.