Imagine there are lots and lots of birds in the world. Some birds live in warm places, some in cold places, some near the ocean, and some in the mountains. A bird atlas is like a giant book that shows us where all of these different birds live and how many there are.
People who study birds use the bird atlas to help them find out about the different kinds of birds all over the world. They look at the maps and information in the atlas to figure out which birds live where and how many of them there are.
The atlas also helps people who like to watch birds. They can use the atlas to find out where the best places are to go and see different birds. So in a way, the bird atlas is like a treasure map that helps people discover all the wonderful feathered creatures that live in the world.