Pseudo-random ensemble is like a box of random things that are all connected in some way. Think of it like a box of puzzles pieces: each of the pieces looks different and aren't the same shape, but they all fit together to make a complete picture.
Pseudo-random ensembles are collections of different numbers, objects, or things that all have something in common. When the pieces are put together randomly, they can be used to do something, like predict the weather or solve a math problem. It is like a jigsaw puzzle where all pieces are different but are connected in some way.