An annotated bibliography is a list of sources (such as books, articles, and other materials) you’ve found for your research. Each entry includes two parts:
The citation, which gives full publication details of the source.
The annotation, a brief paragraph (typically around 150 words) that explains what the source is about and its relevance to your project.
Think of your sources as being in conversation with each other and how they will be useful to you. Your sources will give you certain background information, exemplify different approaches or arguments, or demonstrate different methods or approaches. Each source will make a contribution or serve a purpose. If not, think about why you're including it.
You should write an annotated bibliography for several reasons. It will help you to:
Don't copy the author's abstract or summary. Paraphrase and focus on what is relevant to your project and approach.
The Purdue OWL website provides a good description of annotated bibliographies.
The site also includes example annotations. Your own annotation will be shaped by the sources you're using, but the example can be helpful for structure and tone.