Definition of folders:
(n) :
(computing) A virtual container in a computer's file system, in which files and other folders may be stored. The files and subfolders in a folder are usually related.
(n) :
An organizer that papers are kept in, usually with an index tab, to be stored as a single unit in a filing cabinet.
(n) :
A machine or person that folds things.
(n) :
A folding knife, typically a pocketknife.