Answer:
The term extinction's dictionary meaning, is the process of when a species, plant, or any other term for animal family, goes extinct. In more, basic terms, it means when a certain species of animal dies out completely.
This can happen due to several reasons, some being massive natural disasters. Others die out due to an unknown predator entering an ecosystem in which it doesn't belong, therefore disbalancing it.
Examples of extinct animals are Dinosaurs, but their exact reason for going extinct is unkown, there are only theories.
There are also many animals in danger of going extinct, for example Bees.
Hope this information could be of use to you!