Scroll Bars & Scrollers
Many different application windows have scroll bars to allow you to move the contents within the window.  Scroll bars are found on the right and bottom edges of many windows.  Scroll bars have two components, scrollers and arrows.  You can click on a scroller or arrow to reposition the viewable area of a window "up or down" or "left or right".  For example, the scrollers (blue) and arrows are shown in the following image:

 

 

Scroll Bars are used to alter the viewable area for a window as demonstrated below (observe how by simply moving the position of the scrollers the viewable area within the window is altered):

Move & Position
Most windows can be moved and repositioned on the Desktop.  All you have to do is select it and drag it to the desired location.  Note that most windows require that you click on the window's Title Bar to move it.  An exception to this rule are Finder windows.

Note that some applications can have several component windows visible at any give time.  For example, Microsoft Word 2004 for Mac as shown below has both a Document window and a Formatting Palette open.  Either or both can be moved and placed in a desired location on the screen.

 

Resize
Resizing windows is easy.  Look at lower right corner of the first image in this guide and you will notice a triangular icon.  This is known as the Resize control.  Just click on the Resize control with the mouse and drag it to adjust the window's size (larger or smaller).  Many Mac OS X applications implement window resizing and some will even adjust the size of the window contents as you resize the window.