What is an annotation?
"An annotation is a short description of an item. Annotations describe (summarize important content) and evaluate (critically analyze) the resource based on standard criteria. An annotation differs from an abstract or summary, as abstracts and summaries usually only describe or summarize the content and do not critically evaluate. Annotations may be written to describe books, Web sites, articles, government documents, videos, or other items."
From the Weber State University's Stewart Library.