According to HowStuffWorks, the main difference between DVD ROMs and CD ROMs is that DVDs hold 4.7 gigabytes and CDs have 650 megabytes. Two-layer DVDs hold twice as much as a regular DVD.
The phrase "DVD-ROM" stands for "digital versatile disk read-only memory," and "CD" simply stands for "compact disk." According to HowStuffWorks, the extra memory on a DVD adds considerable enhancement to movies, including six channels for audio instead of only two. DVDs also have significantly higher quality for video since they have the ability to store much more data. DVDs often hold 2 million pixels for HD, where video CDs only hold as many as 85,000 pixels. DVDs have higher compression quality as well, since they use MPEG-2 instead of the MPEG-1 codec. MPEG-2 is capable of much higher quality in video recording than MPEG-1. DVDs are capable of carrying as much as 133 minutes of high-resolution video with 720p resolution. They also often contain extra information, such as subtitles in 32 languages. Many DVD movies have more sophisticated menus as well. It is often possible to choose bonus material on DVDs, which is not possible on a video CD, since the CDs do not have as much room.