An annotated bibliography provides summaries and evaluations of sources, while a traditional bibliography is just a list of citations for sources. As long as you keep this key difference in mind, making an annotated bibliography is totally doable. The citation for each source is followed by a description and discussion of the source, called the annotation. These annotations typically explain the strengths and weaknesses of the sources, as well as their relevance to your research project. Always check with your teacher or advisor for precise instructions.
As you now know, one annotation does not fit all purposes! There are different kinds of annotations, depending on what might be most important for your reader to learn about a source. Your assignments will usually make it clear which citation format you need to use, but they may not always specify which type of annotation to employ. In that case, you’ll either need to pick your instructor’s brain a little to see what she wants or use clue words from the assignment itself to make a decision. For instance, the assignment may tell you that your annotative bibliography should give evidence proving an analytical understanding of the sources you’ve used. The word analytical clues you in to the idea that you must evaluate the sources you’re working with and provide some kind of critique.