Custom Document Property Sets are user defined information sets that can be attached to folders, documents and users. They are used to further define the document, folder or user.

A common use for this feature is to allow documents to be searched based on custom information, rather than just their name or content.
Custom Properties can be defined globally or at the library level. This allows you to create a custom document property set that only appears in one or selected libraries. This way, "Custom Property Sets" that do not apply to certain libraries can be hidden from view.
See also:

Examples and usage scenarios of Custom Document Properties

How to create Custom Document Property Sets

Next Topic is Creating Custom Document Property Sets