I can't really explain it with words, so I'll just use an example if that's alright.
Imagine I have made several marbles, maybe something like "Pizza", "Spaghetti", "Ramen", and "Fried Chicken" along with their own textures. I wanted a feature that could save all of those marbles, so the next time I open the game, I can load those specific marbles again.
This way I can reuse the same marbles over and over again, without recreating them one by one.