A Quick Introduction to Your Dock in OS X Yosemite
Take a minute to look at the row of icons at the bottom of your display. That row, good friend, is the Dock, and those individual pictures are known as icons.
Icons in the Dock and Launchpad are odd ducks; you activate them with a single click. Most other Finder icons are selected (highlighted) when you single-click and opened only when you double-click them. So Dock icons (and their Launchpad brethren) are kind of like links on a web page; you need only a single click to open them.
Here’s the rundown on what happens when you click Dock icons:
If it’s an application icon, the application opens and becomes active. If the application is already open, it becomes active, which brings it and all its windows to the front.
If it’s a document icon, that document opens in its appropriate application, which becomes the active application. If that application is already open, it becomes the active application with this document in the front.
If it’s a folder or disk icon, a stack, fan, or grid with its contents appears so you can pick an item. If you choose Show in Finder from this menu, the folder’s window opens in the Finder.
If the item is open already when you click its Dock icon, it becomes active.
By default, the Dock contains a number of commonly used OS X applications, and you can also store your own applications, files, or folders there.
But first, look at the items you find in a standard OS X Yosemite Dock. If they aren’t familiar to you, they certainly will be as you get to know your Yosemite.
It’s likely that your Dock won’t look exactly like the one shown. If you added icons to your Dock before you upgraded to Yosemite, for example, you’ll see those icons. If you have any iLife (iMovie, the soon-to-be-retired iPhoto, or GarageBand) or iWork (Pages, Numbers, or Keynote) installed, or you get a new Mac with Yosemite preinstalled, you may see their icons in your Dock.
And if you’ve ever deleted one of the default icons shown from your Dock, it won’t “come back” when you install Yosemite.