Special Features

• Special features (or "bonus features"/"extras") include anything beyond the film itself, like interviews or commentary. Sometimes technical features (like the audio format or the aspect ratio) will be misleadingly described as "special features".
  
  

Aspect Ratio

• The description on the case will either offer a numerical ratio (ex: 1.85:1, 2:35.1) or "Widescreen" vs. "Full-Frame"/"Standard." Consider whether or not the film has been "modified to fit your screen" (which usually means horizontal cropping to make the image more square).
  
  

Region and Edition

• The DVD region is relevant if you plan to watch the DVD in another country. Region 1 DVDs will only play in the U.S., not in Europe or Asia, according to Home Theater Info.
  
  Remember that "Special Edition" may just be a marketing device; a "special" edition may not differ substantially or at all from an earlier edition.