A star atlas is like a really big map of the night sky. It shows all the stars, planets and other things in space that you might be able to see with your eyes or a telescope. It's a bit like the maps that show roads and places on Earth, but instead it shows all the cool things that are up in the sky. You can use it to find your way around and locate stars and planets that you want to look at. Just like a map, it can be really helpful to have a guide or someone who knows how to read the star atlas well so you can find everything you want to see.