Swampman is a super duper silly idea that a really smart philosopher guy named Donald Davidson came up with to help explain something tricky called the problem of personal identity.
Let's pretend that you're walking through a swamp (ewww, yucky!) and all of a sudden, a big bolt of lightning comes out of the sky and strikes you! But here's the really weird part - the lightning bolt zaps you SO hard that it completely destroys you down to every little tiny piece!
Now, let's say that at the exact same moment that the lightning bolt hit you, there was a bunch of mud and water splashing around right where you were standing. And because of the lightning bolt, the mud and water suddenly took the shape of a perfect copy of you with all of your thoughts and memories!
This muddy copy might look exactly like you, sound like you, and even think like you, but there's one big problem - it's not really YOU. It's just a brand new thing that happens to look and act like you did before you got zapped by lightning.
So the question that Swampman brings up is this: Are YOU still YOU even though your muddy copy looks like you and thinks like you did before you got struck by lightning? Or are you something different now that you've been totally and completely destroyed by the lightning bolt?
This might sound really crazy and confusing, but it's a really important question for people who try to understand what makes us who we are. So if you ever hear someone talking about Swampman, just remember that it's all about trying to figure out what makes us who we are, even if it means talking about silly things like muddy copies and lightning bolts in swamps!