An annotated bibliography is a list of books, articles, and other research sources, each with brief notes about the source's content and relevance to your research. They can be useful when you're still researching ideas for a paper, for when you've finished a first draft and need more sources, or just when you want to learn more about a topic and remember what you've learned.
Writing down what you've read and where you've read it when you're looking at a source is a lot easier than trying to find the source again later, so it's good to get in the habit of doing it while you're researching. An annotated bibliography is a great way to make sure you have everything down in one place. Another way to think of it is like you're making a research log so you can keep track of what things you've read and the most important points in each.
One of the most important things about an annotated bibliography is how you list the sources. Instead of just writing down the title and author, you need to create a citation for each source.
A citation is like a formula that makes it as easy as possible for someone else to find the book or article you read. One way to think of them is that they're like breadcrumbs which another researcher can follow to find out more about your topic if they're interested in it.
In a classroom setting, citations are important because they let your professor know where you got your information. If you don't cite your sources in a paper, you can be accused of plagiarism, or stealing someone else's work. There are a few different citation styles, and the one you use will depend on the subject, so be sure to ask each professor which style they prefer.