A bibliography is a list of sources (books, journals, websites, periodicals, etc.) that have been used for researching a topic. A bibliography usually just includes the bibliographic information (author, title, publisher, etc.).
An annotated bibliography is a list of sources that gives the publication information and a short description — or annotation — for each source.
An annotated bibliography shows that the author has understood the sources used during their research on a topic and gives the reader enough information to decide whether they should read the specific work.