Symmetric set

A symmetric set is like a box of toys where every toy has a friend that's exactly the same, but they might not be next to each other in the box. Just like how you have a left hand and a right hand that look the same, but they're on opposite sides. So, if you look at the box of toys, you might not see the same toys next to each other, but if you look closely, you'll see that every toy has a friend that's exactly the same somewhere in the box. That's what makes it symmetric!