The Sega 32X was not a console in itself, but a short-lived add-on introduced in 1994 for the Sega Mega Drive. It allowed users to play 32-bit games on the 16-bit Mega Drive, to extend the life of the Mega Drive system whilst the user base of the Sega Saturn grew.
Sega 32X cartridges are plugged into the 32X unit, and Mega Drive cartridges can also be used in the 32X, allowing it to be permanently attached to the Mega Drive.
32X cartridges are fundamentally the same as Mega Drive cartridges with some small differences in the plastic casing.
The last games for the 32X were released in 1996, but the system itself was cancelled in 1995 so Sega could concentrate its efforts on the Saturn.