Hello!
An annotated bibliography consists of two things: your sources/citations, and summaries.
To write an annotated bibliography essay, you need to cite your source and write a brief summary about what the source is talking about. If you have multiple sources, you must cite and summarize each of them, mentioning their key points.
For example, if you found an interesting article in a magazine, you could cite the article, and then write a brief summary about what the article was about in your own words.
I hope this helps you! Let me know if you have any more questions!
-Mal
