This was Sega's first add-on to the Sega Genesis. The theory behind this move was simple.
CDs are cheaper than cartridges and CDs have a greater data capacity than cartridges.
At the time, the Sega Genesis was the most popular 16-bit console and therefore, the market for this new device was huge. Eventhough three million units were solded world wide, the invasion did not turn out as planned. The Sega CD had many remarkable flaws. It suffered from an extremely slow loading process and a lack of quality software. And its slow loading process plagued the unit with annoying 10 to 20 second load times verses the instant load time found on the Genesis.