What do you understand by the biodiversity or biological diversity?

Starting from micro-organisms and bacteria, lichens to banyan trees elephants and blue whales. This entire habitat that we live in has immense biodiversity. We humans along with all living organisms form a complex web of ecological system in which we are only a part and very much dependent on this system for our own existence. For example, the plants animals and micro-organisms re-create the quality of the air we breathe, the water we drink and the soil that produces our food without which we cannot survive and this dependence on other known as biodiversity.