Vavilovian mimicry is when a plant or animal looks like another living thing in order to stay safe. This is like when you dress up for Halloween to look like your favorite superhero or princess.
For example, some plants look like other plants that are poisonous, so animals won't eat them. Similarly, some animals, like butterflies, look like other animals that are poisonous, so predators won't try to eat them.
But why do plants and animals do this? Well, it's because they want to survive. By looking like something else that's not harmful, predators won't try to attack them.
So just like how you dress up for Halloween to be safe from scary monsters, some plants and animals pretend to be something else to stay safe from their predators.