Bibliography can be a part of the book, concept paper, etc., wherein you can find the sources of those certain topics you had read and had learned. The sources can be found in another book, newspaper, magazine or URLs in the internet. Bibliography is important because, for example in a concept paper, the readers or the viewers would know how did you come with that specific explanations about the topic or how did you know such an information or they can also know where to find those pieces of information and at the same time, to prove if you really had a research and to know if you did some plagiarizing or nah. That's why bibliography is very important as being a part of the book. (Sorry for explaining this long. I know you didn't asked why bibliography is important but it's just for some more information and at the same time, for us to understand more about a word in the world named bibliography).