6.1. What Are Libraries?
Libraries are lists that are essentially known by the kinds of files they will contain: documents, pictures, forms, and wiki documents.
There are four different types of libraries:
Using the name "Document Library"for this type of library rather obscures what it really is. A Document library is a list that creates a new file of some type whenever you create a new list item. The file type depends on what template you associate with the list itself (and doesn't have to be a document template). If you enable content types, the file type depends on what type of library list items (and their associated template) you want to have available for the list. This list also has features such as content approval, ...