Released back in 1987 under the name PC Engine in Japan the system was made by NEC Corporation and used two 8-bit cpu's for power (hence the 16, 8 X 2). This system was later released in america in 1989 under the name TurboGrafx 16. Unlike many earlier systems this one did not take a traditional cartridge. It used what was called a TurboChip (HuCard in Japan). Basically the games would be on cards the size of a credit card which slid into a slot on the front of the system. Another thing that made this system a bit different then all others is it only had 1 controller port, You had to buy a TurboTap to play more then 1 player. Each game came in a cd case with a protective sleave on the card. The graphics quality of the system falls somewhere between the nes and snes (TG16 had a sligtly larger color palett then the Genesis).
About a year or so later NEC released a Compact Disc add-on for thier system which basically was a single speed cd-rom drive. This drive not only provided more storage space but cd quality audio and full motion video. To play a cd game you needed what was caled a system card. This card would tell the system to run the game off a cd-rom instead of card. There were even much more powerful cards that made better games run.
At the end of the day, like the Sega Saturn, NEC's system did well in japan but not so well in the usa due to the popularity of the Super Nintendo and Sega Genesis. Turbo Grafx had its share of great games which many will never know. Here is some information about The Turbo Grafx: