A bibliography is like a list of all the books and sources that someone used to learn about a certain topic, like the Sierra Nevada mountains. It's kind of like when you make a list of all the books you read in school.
The Sierra Nevada mountains are really big and have a lot of different things in them, like trees, animals, and rocks. Lots of people have studied the Sierra Nevadas and written things about them, so a bibliography is a way to keep track of all those books and articles.
A bibliography might include the author's name, the title of the book or article they wrote, the date it was published, and maybe even some quotes or parts of the book that are important to understand the Sierra Nevada mountains better.
So, if you want to learn a lot about the Sierra Nevada mountains, you can look at their bibliography to see all the things other people have learned and written about them.