Okay, let's imagine you have a bunch of toys, like balls and blocks, that you want to rearrange into different orders. For example, you might want to put the red ball before the blue block, or have the yellow block first and the green ball second.
When you do this, you're basically making permutations - different ways of arranging the toys in a certain order. And a Hopf algebra of permutations is a fancy math thing that lets you do all sorts of cool calculations and transformations with these permutations.
It's kind of like having a magic toy box that can do all sorts of tricks! You can add, multiply, and divide permutations. You can create new permutations by combining old ones. And you can find special properties of the permutations, like which ones are invertible (meaning you can reverse them) or which ones have unique representations.
Now, the actual math behind this is pretty complicated and probably too hard for a five-year-old to understand. But just remember that a Hopf algebra of permutations is like a special set of tools that helps you work with collections of things that can be rearranged in different orders. And those tools let you do some really neat stuff that might make your head spin, but is still super cool!