A bibliography is a list of citations for your sources (books, journals, websites, periodicals, etc.). It's like a Works Cited page at the end of a paper -- listing your source's author, title, publisher, etc. (usually in MLA format).
An annotation is a paragraph that goes underneath each citation. It usually includes a short summary of the source, an evaluation of the source's credibility, and an assessment of how you're going to use the source (or not) in your research paper. (See below for more information).