An annotated bibliography is a list of sources on a certain topic with a brief description of each source.
Each entry in an annotated bibliography should include all the information normally included in a list of works cited. For instance, the citation for a book would include the title, author, publisher, place of publication, and year of publication. Use the appropriate bibliographic format for citations (such as MLA, APA, Turabian) as specified by your instructor.
The bibliographic information is followed by an annotation, which can be a few sentences or a lengthy paragraph that describes (or, in some cases, evaluates) the contents of the source. If you have questions about how detailed or evaluative the annotations should be, ask your instructor.
Here's an example of an entry from an annotated bibliography, with the citation of the book in Turabian style and a brief description of the book:
Garrow, David J. Protest at Selma: Martin Luther King and the Voting Rights Act of 1965. New Haven: Yale University Press, 1978.
Garrow describes how the strategy of protest employed by Martin Luther King, Jr., and SCLC at Selma influenced the emergence of the Voting Rights Act of 1965. He contends that the choice of Selma as a site for civil rights protests and the specific tactics that SCLC adopted in Selma were part of a plan to force the introduction and passage of national voting rights legislation. The foremost consideration in this campaign was the need to elicit "unprovoked white violence aimed at peaceful and unresisting civil rights demonstrators." Garrow argues that at Selma "a strategy that bordered on nonviolent provocation supplanted the earlier belief in nonviolent persuasion." SCLC correctly assumed that police violence would generate national media coverage and this, in turn, would stimulate reactions "throughout the country, and especially Washington," leading to pressure for federal voting rights legislation.
(Example from: The Civil Rights Movement: References and Resources, by Paul T. Murray. New York: G.K. Hall & Co., 1993.)