A tabbed folder standing for a container of files.
Also known as: Directory icon
A rectangle with a raised tab along its top edge stands for a directory. The tab is what distinguishes it from a plain document, and it comes from the manila folders of a filing cabinet.
A wide rectangle whose top edge steps up over its left portion to form a raised tab, the whole read as a folder seen from the front.
Both are built from objects, and both are used in software contexts.