An annotation is a short description of a resource such as a book, article or website. Many annotations are also evaluative. They may comment on the quality or usefulness of the resource.

Here is an example of a website annotation:

Purdue's Writing Lab
Purdue University's Online Writing Lab is often cited as the best one on the World Wide Web. Browse its large collection of "handouts." Some of the topics include outlining, writing a research paper, punctuation, argumentative writing, writing essay exams, writing definitions, and writing a thesis statement.