In the world of ecology, association refers to how different living things interact with each other. It's kind of like how you play with your friends at school or how your pets interact with each other.
Just like how you might have a best friend you like to hang out with, living things in nature also have friends that they prefer to be around. For example, some types of birds might prefer to hang out with other birds of the same species because they understand each other's communication better. This is called a "positive association" because the birds are benefitting from being together.
On the other hand, some living things might not get along and try to avoid each other. For example, some plants might release chemicals that repel insects so that they don't get eaten. This is called a "negative association" because each organism is trying to protect itself.
There are also cases where two living things might not affect each other at all. This is called a "neutral association." It's kind of like when you see a person walking their dog on the sidewalk - you might not have anything to do with each other, but you also don't bother each other.
Overall, association in ecology refers to how different living things interact with each other, whether positively, negatively, or not at all.