The CD-i 210 was a stripped down version of the CD-i 220, lacking the chique opening door in front of the tray. Also, its FTD-display was slightly less sophisticated. Several versions of the CD-i 210 have been produced, each with minor differences (shell version, digital video cartridge compatibility model, CD loading mechanism version, etc). But the CD-i 210 is nowadays certainly the most common CD-i system found worldwide.
The CD-i 210 is thus part of the big CD-i family. CD-i is short for Compact Disc Interactive. It is an interactive multimedia system combining moving and still video, audio and program content on a compact disc, which can be played back in a dedicated CD-i player.
CD-i was jointly developed by Philips Electronics NV and Sony Corporation in the mid 80s. Together, both companies defined CD-i's basic specifications in what is know as the Green Book. They decided to use the well-tested OS-9 operating system from Microware Systems Corporation, which was designed for embedded, real-time applications. Microware was also heavily involved in the CD-i design process. Eventually, Philips took the biggest part in the development process, being responsible for at least 90% of CD-i's development.
The basic CD-i specification allows a CD-i player to display full screen animations in 128 colors over a 16.7 million color background, or play partial screen moving video in a lower framerate in 16.7 million colors, both with accompanying sound. However, these capabilities are extended when a Digital Video cartridge is placed in the player. In this case, the player is able to display full-screen, full moving 30 fps video in 16.7 million colors according to the MPEG-1 standard. Although Digital Video is not a part of CD-i's basic specification, it is generally considered to be a "must-have" extension to a CD-i player since it adds an enormous audiovisual performance boost to the system.
A Base Case CD-i player should be able to decode standard PCM audio as specified for CD-Audio, as well as a dedicated audio coding scheme called ADPCM, or Adaptive Delta Pulse Code Modulation. A CD-i player equiped with a Digital Video cartridge is also able to decode MPEG-1 layer I and II audio.
CD-i can display both main planes in either normal, double or high resolution, which are 384x280, 768x280 and 768x560 respectively. CD-i highest resolution (768x560), used for QHY images, is the highest resolution that can be made visible on a normal TV set, so CD-i takes TV-technology to its edges.
Note that there are no system performance differences between the various players. Although there are various models of CD-i players, every CD-i disc will perform exactly the same in terms of system speed or audio and video quality on every CD-i system.
Info compiled from the excellent CD-i FAQ 2000 Edition. If you want to know more about CD-i, go there !