A Descriptive annotation may summarize:
This type of annotation seeks to answer the question, Does this source cover or address the topic I am researching?
An Informative annotation:
This type of annotation seeks to answer these types of questions, What are the author's main arguments? What conclusions did the author draw?
An Evaluative (also critical) annotation includes value judgments or comments on the effectiveness of the work. In this context, critical means evaluative and may include both positive and negative comments. A critical annotation may contain the information found in a descriptive annotation and discuss some of the following features:
This type of annotation seeks to answer these types of questions:
Combination is the most common style of annotated bibliographies. It include a general overview of the article, like in the descriptive; a critical analysis and judgement of usefulness, qualification & bias of the author, and strengths/weakness of the text (like the Evaluative); and information about the research/results (informative).