You already know that a bibliography is a list of works cited or otherwise relevant to another work. The word also refers to the study of books as physical objects, without any special regard to their meaning. Bibliographers study the way books were printed and bound, and usually begin a description of a book with its format — that is, its size and means of construction. By tracking other physical details — the nature of the type, the kind of paper (often determined through a study of chainlines and watermarks), the binding, and the variants among different editions and issues — they can make inferences about the conditions of publication (and sometimes authorship).

Bibliography is a kissin' cousin of textual criticism, the work of establishing a text by sorting out the variants in the surviving witnesses.

From the Guide to Literary Terms by Jack Lynch.
Please send comments to Jack Lynch.
Note: This guide is still in the early stages of development.
Three question marks mean I have to write more on the subject. Bear with me.