A bibliography is a list of sources that you have put together in the course of doing research and writing your paper. Sources in a bibliography can vary but usually include materials such as books, journal articles, newspapers (i.e. periodicals) and web sites among other resources. Information included in bibliographies are usually material such as the author, title, and publisher of the work being included, set in a proper citation format such as APA or MLA style. An annotation is simply a note or comment attached to any sort of data such as text or an image.
An annotated bibliography is a collection of sources you put together, listed in a proper citation format with a summary or comment on the mentioned source included.
A man and woman riveting team working on the "nuts and bolts" of the cockpit shell of a C-47 aircraft (1942) Link
Remember when putting together your annotated bibliography to include the following:
Annotations in the Margins made to the work of Saint Augustine (Link)
An abstract is a short summary included in the beginnings of papers to describe what the paper is about to a potential reader. It is descriptive only. Annotations are descriptive as well but they are also more than that; they include discussion and sometimes criticism of the source on a variety of issues such as whether the source is well written or if you found the argument made in the source to be convincing or not.
A critical annotation will judge the source in question; it can include positive and negative comments. For instance a critical annotation could talk about the tone or bias of the author in the source and whether it was helpful or not in proving its thesis. Or for example a critical annotation could question the accuracy of the source or talk about omissions made by the author that helped or hurt the source in question.
A descriptive annotation is usually just a summary. For instance a descriptive annotation could summarize what the source in question is trying to prove or it could simply state what the conclusions of the author were at the end of the work. It could simply focus on the research methods used in the source or just what the source is supposed to be about overall.