Bibliographies are lists of resources, usually books. Be sure to differentiate carefully between BIBLIOgraphies, lists of citations, and BIOgraphies, which are the nonfiction lives of people.
Bibliographies are normally used by people researching a subject, and by librarians building a collection. They have a rather narrow audience but are quite irreplaceable if you are the one needing to do the research.
There are two large categories of bibliographies: annotated and unannotated. Annotations are just like abstracts -- short summaries of the material. So annotated bibliographies could also be referred to as abstracts, but are not since abstracts are usually understood to be annotated indexes.
Go to the PAC library catalog and do a keyword search for "bibliography or bibliographies" and you will find that most bibliographies are about a subject. Take a look on the shelf at the following titles:
The Old Army in Texas
The humanities : a selective guide to information sources
Best books for young teen readers, grades 7 to 10
Contemporary African American novelists
Nuclear proliferation : an annotated bibliography
Divorce : the best resources to help you survive
The ultimate business library
Hispanic surnames and family history
You get the idea. The current PAC catalog lists 1,525 bibliographies, so you are apt to encounter them when you do a subject search.