A hybrid DVD refers to:
A disc works in both DVD-Video players and DVD-ROM PCs. More usually it is called an enhanced DVD
A disc that has a foreign language dubbed audio track and also has subtitles in that language.
A DVD-ROM disc runs on Windows and Mac operation system. More usually it is called a cross-platform DVD.
A DVD-ROM or DVD-Video disc also contains Web content for connecting to the Internet. More usually it is called a Web DVD or Enhanced DVD.
A disc is with an embedded memory chip for storing custom usage data and access codes. More usually it is called a chipped DVD.
A disc with two layers on one side and one layer on the other. More usually it is called a DVD-14.
A disc contains both DVD-Video and DVD-Audio content or SACD content. More exactly it is called cosmic or AV DVD, which is supported by DVD-Audio standard. The SACD standard does not officially allow video. So it is hard to say whether a SACD player will do with a hybrid SACD+DVD-Video disc. Other variations of this hybrid would be a disc with both DVD-Audio and SACD content, or a disc with all three formats.
A disc with two layers or two sections one containing pressed (DVD-ROM) data and one containing rewritable (DVD-RAM or other) media for recording. More usually it is called a DVD-PROM, mixed-media, or rewritable sandwich disc.
A disc that with two layers, one can be read in DVD players and the other can be read in CD players. More usually it is called a legacy or CD-compatible disc. There are at least three variations of this hybrid, although most aren't commercially available.
A 0.9- to 1.2-mm CD substrate bonded to the back of a 0.6 mm DVD substrate. One side can be read by CD players, the other side by DVD players. The resulting disc is 0.6 mm thicker than a standard CD or DVD, which can cause problems in players with tight tolerances, such as portables. Sonopress, the first company to announce this type, calls it DVDPlus. It's colloquially known as a fat disc. There's a variation in which an 8-cm data area is embedded in a 12-cm substrate so that a label can be printed on the outer ring.
A 0.6-mm CD substrate, with a special refractive coating that causes a 1.2 mm focal depth, bonded to the back of a 0.6 mm DVD substrate. One side can be read by CD players, the other side by DVD players.
A 0.6-mm CD substrate bonded to a semitransparent 0.6 mm DVD substrate. Both layers are read from the same side, with the CD player being required to read through the semitransparent DVD layer, causing problems with some CD players. The trick is to make the semitransparent layer "invisible" to 780-nm CD lasers. This is the format used for hybrid SACDs.
A 0.6-mm DVD substrate bonded to a CD+DVD hybrid substrate. This disc would be readable by SACD and CD players on one side and by standard DVD players on the other, since most standard DVD players are confused by a hybrid disc with only a semitransparent layer.