An annotated bibliography is a list of citations to sources, such as books and articles. Each citation is followed by an annotation, a brief descriptive and evaluative paragraph, about 150 words long, that analyzes the source. An annotated bibliography usually looks like any other bibliography with alphabetized citations of sources, except that here each source is followed by an explanatory paragraph. This work can form the basis of a literature review later in the writing process. The purpose of the annotation is to inform on the relevance, accuracy, and quality of the sources cited.
An annotation is not only a summary of the source in question. It should be a short but critical analysis as to why and how the source fits into the larger research question. An abstract functions as a summary, an annotation should be contextual to the specific topic at hand. It should be both descriptive and evaluative.