Let's break down the definition:

• An annotation is a summary and evaluation of a source. While an abstract includes only a descriptive summary, an annotation includes a summary and critical analysis.
• A bibliography is a list of sources (books, journals, etc.) used in researching a topic. Bibliographies are sometimes called "References" or "Works Cited."

An annotated bibliography, therefore, consists of a bibliography as well as a summary and analysis of each source. 

Annotated bibliographies may include:

• Summaries: Summarize the source in your own words. What is this article/book about? What are the main arguments? What topics are covered?
• Assessments: Evaluate the source. Is it useful? Is the information reliable? How does it compare with other sources in your bibliography?
• Reflections: Discuss how the source fits into your paper. Is it helpful to you? How does it help you shape your argument? Has it changed how you think about your topic? 

Before you begin your annotated bibliography, ask your instructor to clarify assignment guidelines, such as preferred citation format, types of sources, and annotation length/features.

• Bibliographic citations are generally formatted in MLA or APA.
• Entries are alphabetical by the last name of the author (or title) in each citation.
• Annotations are written in paragraph form with full sentences.
• Third person is preferred, but first person may be used for personal reflection.
• Annotations are usually a single paragraph (100-150 words) long, but may vary from a couple of sentences to a couple of pages, depending on the source and the assignment.

While it is important to have a general idea of your topic before you start your research, creating an annotated bibliography may help you formulate a clearer thesis. By reading each source carefully and critically, you will have a better idea of the issues that others are addressing about your topic and should be able to develop your own point of view more clearly.