Filesystem:/private/var/stash

Why does this folder exist?
Cydia creates this folder to increase the amount of files allowed on the system partition. Since this file is on the user data partition, items are symlinked to certain subfolders inside this folder so you can put many more files on the system partition.

Files
No files are under this folder.

Folders
Applications (Where the system applications are stored)

Library (Contains system ringtones/wallpapers)

Themes.XXXXXX (Contains WinterBoard themes)

Certain other items from Cydia that are made by Saurik store their files here as well.