A descriptive annotation summarizes the source. It describes the source's core thesis. It mentions the key features of the author's research and the conclusions drawn by the author, but does not offer personal commentary or analysis of the source.
Instead of merely summarizing a particular source, an evaluative annotation offers personal analysis of author's expertise, research methodologies and conclusions. This type of annotation may also compare and contrast the source to other previously cited sources and discuss the overall usefulness of the information.
This type of annotation is similar to the descriptive annotation in that it provides information about the content of the cited source. Unlike the descriptive annotation, this annotation only provides general information about the content without describing or discussing the core thesis or argument posed by the author. An example of its use would be to describe how the information is organized or mention specific chapter titles.
This form of annotation utilizes elements of the other types. For example, the annotation may begin with a straight summary and follow it with a critical evaluation, or include general content information. The combined annotated bibliography is the most commonly used.