"An annotated bibliography is the full APA Reference of a source followed by notes and commentary about a source. The word “annotate” means “critical or explanatory notes” and the word “bibliography” means “a list of sources”. Annotations are meant to be critical in addition to being descriptive."
Below are very useful websites and guides to help you format an APA annotated bibliography.
Annotated Bibliography Samples -- From Purdue OWL
Annotated Bibliography Basics -- Eastern Nazarene College