The 2007 edition marks a major new release of the venerable Office suite, and requires some explaining. This demo video from Microsoft is a bit rah-rah, but it explains what's new and how its feature set trumps that of older versions of Office. Look for the chapter menu at lower left in this rich video.
A free alternative to Microsoft Office is OpenOffice by Sun Microsystems. Martin the Librarian offers an introduction to this powerful and mostly-Office-compatible productivity suite. If you haven't experienced a YouTube video yet, just click on the Play button below. You may have to hit it twice: