The Default Application
In Mac OS X, the Finder is the default program.  In fact when you complete the initial setup with Setup Assistant or log into your machine after it is booted, Mac OS X logs into the Desktop but only Finder is active.

By default Mac OS X is configured to have only a single Finder window open at a time.

You can perform a Spotlight search directly from any OS X Finder window.

By default, every Finder window contains a Finder Toolbar, a row of icons each associated with a specific action or display option.  Here's a default toolbar in Mac OS X Tiger:

You can customize the Finder Toolbar to your liking.  You can add or remove icons and adjust the size of the toolbar.

If you don't want to have the Finder toolbar visible you can hide it.  There are two easy ways to make it go away or reappear.

Burnable Folders are folders make it easy to burn CDs or data DVDs directly from a Finder window.  This feature is made possible with a folder type called a "Burn Folder".

Finder Slideshows allow you to create and view images as a slideshow and kick them off directly from the Mac OS X Finder.  If the image size is large enough, you'll be able to see the images full-screen.

The Finder and Sidebar co-exist in Finder Windows.  The Sidebar resides on the left side of any Finder Window.

Finder Windows give you flexibility in how they present items to you.  For example, you can view items by Icon, List, or by Column.

Thanks to the Aqua user interface you have different options to browse through your system with simple clicks of the mouse and keystrokes.  If you prefer the command line you can launch the Terminal applications and browse with keystrokes.

You can adjust the size of Finder icons and text.  The modification options shown to you by Mac OS X will depend on the Finder view you are currently using.  The examples shown in this guide have been performed on the Applications Folder.