An annotated bibliography is a list of citations. Under each citation is a paragraph of about 150-250 words summarizing and evaluating the resource. Below are some helpful websites about writing annotated bibliographies:
How to Prepare an Annotated Bibliography | Cornell University Library (Written by Michael Engle, Amy Blumenthal, and Tony Cosgrave from Olin Library Reference, Research & Learning Services, Cornell University Library)
Annotated Bibliographies | The Writing Lab & The OWL at Purdue (Written by Dana Bisignani and Allen Brizee from The Writing Lab & The OWL at Purdue, Purdue University)
An example of an annotated bibliography written in APA style can be found here.