Broadly, the systematic study and description of books.
The word can refer to the listing of books according to some system (called descriptive, or enumerative, bibliography), to the study of books as tangible objects (called critical, or analytical, bibliography), or to the product of those activities. The purpose of bibliography is to organize information about materials on a given subject so that students of the subject may have access to it. A descriptive bibliography may take the form of information about a particular author's works or about works on a given subject or on a particular nation or period. Critical bibliography, which emerged in the early 20th century, involves meticulous descriptions of the physical features of books, including the paper, binding, printing, typography, and production processes used, to help establish such facts as printing dates and authenticity.