.DS_STORE File Extension

Stores viewing preferences for a folder in Mac OS X; includes information about the folder's window location, window size, what view option has been selected (icon, list, or column), and the layout of icons in the window.

DS_STORE files are usually invisible, but may become visible when copied over a network, copied to a Windows computer, or restored from a backup. The DS_STORE file can be deleted from within a folder without affecting any of the data inside the folder. If the DS_STORE file is removed, the folder will open using the Finder's default view settings.

DS stands for "Desktop Services."