The Sidebar was introduced in Mac OS X 10.3 (Panther). It appears as a pane of icons along the left side of Finder windows (see Figure 7). It also appears in Open and Save As dialog boxes (see Figure 8).
Like the Dock, the Sidebar is divided into two parts. The top part includes disks or volumes that you can access. By default, the bottom part includes icons for various folders on your computer's hard disk. Don't let the fact that they don't look like folders fool youthe house is your home folder, Applications is the Applications folder, Documents is the Documents folder inside your home folder, and so on.
Interestingly, clicking a volume or folder icon in the Sidebar opens that item in the same window, regardless of how Finder preferences are set for opening folders. For example, as a long-time Mac user, I like the Finder's general preferences set so that when I double-click a folder, the folder's contents appear in a new window. (Yes, that strategy clutters the screen with windows, but I have a big monitor and can deal with the mess.) But when I click a folder in the Sidebar, no new window appears. Instead, the window contents appear in the same Finder window.
There are a number of ways you can customize the Sidebar. One method is to choose Preferences from the Finder menu and click the Sidebar button in the toolbar (see Figure 9). Toggle checkboxes to determine which items appear in the Sidebar. When you're finished, click the window's Close button to save your settings. Simple as that.
Another way to customize the Sidebar is to drag icons onto or off of it. Yes, this is just like customizing the Dock. Just drag a folder to the Sidebar, position it so a blue horizontal line indicates where the icon will be inserted (see Figure 10), and release the mouse button. The icon appears among the others in the Sidebar.
If you drag an icon onto another icon in the Sidebar, when you release the mouse button, the icon you dragged will land in that "target" icon's folder. Although you might want to manage your files with this technique, that isn't the best way to customize the Sidebar.
In case you're wondering, you can indeed include icons for applications and documents in the Sidebar. But that's not really its best use, as you'll see shortly.
A few more notes about the Sidebar. If you think it takes too much screen real estate in a window, you can hide the Sidebar. Just double-click the vertical bar between the Sidebar and the rest of the window to make the Sidebar disappear. You can also drag that vertical bar to change the width of the Sidebar. And clicking the button in the upper-right corner of a Finder window will hide or display both the Sidebar and Toolbar.