Biodiversity is formed from two words “biological” and “diversity”.
It takes in all varieties of life found on Earth (plants, animals, and micro-organisms) as well as to the communities that they form and the habitats in which they live.
Below is a more simple definition for kids
Biodiversity The variety of living things in a given place—whether a small stream, an extensive desert, all the forests in the world, the oceans, or the entire planet