What is Mac OS X Dock ? It’s the beautiful thing on the bottom of your screen, the thing you either love or hate, but the thing you can’t live without after you’ve been using it for a while. It provides easy access to some of the applications on your Mac, displays which applications are currently running, and holds windows in their minimized state.
What are these icons ?
The icons are representing applications you have on your Mac. Some have been placed there during the OS X installation, others are placed there by the user. Sometimes you will see the little black triangle, just below the icon, this means this application is running.