Polyandry is when a woman has more than one husband at the same time. This is different from what you usually see, where a man has more than one wife.
Imagine you have two toys that you really like playing with. You want to play with both of them at the same time, but you only have two hands. So, you ask your best friend to come help you play with your toys. You and your friend can both hold onto the toys and play with them together.
Polyandry is like that, but with husbands instead of toys. A woman might have more than one husband because she loves them both and wants to be with both of them. They all live together and love each other.
This kind of relationship is not very common, but it happens in some parts of the world. In some cultures, it is considered normal, and in others, it is not. But just like how it's okay to play with more than one toy at the same time, it can also be okay for a woman to have more than one husband at the same time.