The Sega Genesis is a 16-bit video game console released by Sega in Japan in 1988, North America in 1989, and the PAL region in 1990. It was sold under the name Sega Mega Drive in the PAL region as Sega was unable to secure legal rights to the Mega Drive name in North America.
The Genesis was the successor to the Sega Master System and was Sega's third home console and second to be sold outside of Japan.
The Mega Drive is part of the fourth generation era of consoles, and the first of its generation to achieve notable market share in Europe and North America. It was the direct competitor of the Super Nintendo Entertainment System, although the Sega Mega Drive was released two years earlier. The Sega Mega Drive began production in Japan in 1988 and ended with the last new game being released in 2002 in Brazil.
Although the Sega Master System had proved a success in Brazil and Europe, it failed to ignite much interest in the North American or Japanese markets, which, by the mid-to-late 1980s, were both dominated by Nintendo's large market shares. Meanwhile in the arcades, the Sega System 16 became a success. Hayao Nakayama, Sega's CEO at the time, decided to make its new home system utilize a similar 16-bit architecture. The final design was eventually also used in the Mega-Tech, Mega-Play and System-C arcade machines. Any game made for the Mega Drive hardware could easily be ported to these systems.
The first name Sega considered for its console was the MK-1601, but it ultimately decided to call it the "Sega Mega Drive". Sega used the name Mega Drive for the Japanese, European, Asian, Australian and Brazilian versions of the console. The North American version went by the name "Genesis" due to a trademark dispute, while the South Korean versions were called Super Gam*Boy and Super Aladdin Boy. The Korean consoles were licensed and distributed by Samsung Electronics.
What's it worth? Take a look at this Sega Genesis price guide: sold listings for a value indication.