Annotated bibliographies are lists of sources with brief descriptions of the sources below each item. Essentially, it is a references list with a descriptive paragraph (or two) below each citation.
An annotated bibliography can help organize resources in preparation for a literature review. Taking the time to write a summary and quick critique of the work can help determine where the resource fits (or doesn't) into your larger argument.
Example of Annotations with APA Citation:
Example of Annotation with Chicago Citation:
(Citation examples came from Purdue's Online Writing Lab).