An annotated bibliography includes a summary and/or evaluation of each of the sources used. Your school/college may well have an 'in-house' style to use.
This is an example of an annotated bibliography below. First, you put the reference, then a very short summary about the main points of the essay. Without the summary, it's just a reference, get it? Hope this helps.
1) Wilson, A.M. (1998). Public Schools Dress Codes: The constitutional debate. Brigham Young University Education and Law Journal p147 Retrieved May 11 2008 from Apollo library (Jiskha site wouldn't allow me post an internet address)
This is an excellent article that examines the constitutional protection of speech and expression as applied to public school dress codes in the United States. It also gives the reader a more in depth look at how school violence and crime has gone down considerably in different schools after the implementation of school uniforms.
It is only a reference if you refer to it (reference out to it) in/from the text. Otherwise it is a bibliography.
Using Nick's example for it to be a reference you would need something like.
...on school dress code (Wilson, 1998)...
in the text of your article.
But you did ask about a bibliography which is the list of book/articles etc. read/used to construct the essay. Sometimes these are grouped by subject or simply in alphabetical order
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Good explanation and example here.