A bibliography is a list of documents—usually published works such as books and articles. Librarians often call the everyday list form an enumerative bibliography: it tries to be as complete as possible within a chosen scope. For historical research, common enumerative types include national, personal, corporate, and subject bibliographies.
Researchers also use annotated bibliographies, which add brief notes that summarize or evaluate each source, and more specialized analytical or descriptive bibliographies that study books as physical objects (printing, paper, binding, and edition). High-quality bibliographies help show both which sources exist and where gaps remain.
Source: Bibliography and Historical Research: Introduction — University of Illinois Library