Dock
In OS X, the Dock is used as a repository for any program or file in the operating system. It can hold any number of items and resizes them dynamically to fit while using magnification to clarify smaller resized items. By default, it appears on the bottom edge of the screen, but it can also instead be placed on the left or right edges of the screen if the user wishes. Applications that do not normally keep icons in the Dock will still appear there when running and remain until they are quit.
