An annotated bibliography combines two elements: a bibliography and annotations. The bibliography is basically your References list. The annotation describes or evaluates each source. It differs from an abstract since you are sharing your opinion about the quality of the source as well as its usefulness to your research topic. Your thoughts will guide other researchers in their decision to use the source or not.
Purdue’s Online Writing Lab (OWL) has produced several excellent overviews that clarify the concept of an annotated bibliography. Remember to follow only the examples that reflect the APA style.