DVD movies you buy at the local video outlet are manufactured with a stamping process (sort of like the way records are made - although the technology is obviously different), whereas homemade DVDs are "burned". This makes the actual physical reflective properties and the way the actual disc reading instructions are recorded on commercial DVD-Video and home recorded DVD formats different.
In order for DVD players to be playback compatible with both commercial DVD-Video and one or more of the home recorded DVD formats, the player has to have both the proper hardware and firmware (operating system) that is able to detect the differences between the various disc formats.
With reference to the compatibility of the various DVD recording formats with standard DVD players, the owner's manual of the DVD player usually lists which DVD recording formats it can play. Almost all DVD players can play DVD-R (except for some older models made before 2000), while most DVD players can play DVD+RW and DVD-RW (video mode) discs. For more details on what this all means, check out my more complete DVD Recorder FAQs
The only playback restrictions with commercial DVD-Video are Region Code and Video System factors. Video System factors affect VCRs as well.
For additional details, check out two of my reference articles:
