Neo Geo was the arcade to play in Japan in the 90s. It was revealed in 1990 by SNK Company and it was sold in Japan only. The arcade computer was advertised as a complete unit you will need with a 24-bit processor. In reality, it had 16/32 bit CPU and an additional processor of 8/16-bit. The co-processor was known as Z80. The Neo Geo also had graphics GPU with 24-bit BUS.
Don't forget that the console was available under MVS or Multi Video System first. This was the original title. Most of the Neo Geo ROMs can be found under this name. The arcade had slots for 6 cartridges which allows for the arcade owners to save space and get multiple games in one console. A player would insert coins and play the desired game. Once the games are obsolete, they can be replaced with new ones. It is important to add that the same system with the same characteristics was available under Neo Geo Rental System. Its original name is different as well and it is AES or Advanced Entertainment System. First, it was available as rental game only due to a high price. Later it was available on the market but the price was still high. As such, this console is today considered as luxury gaming item and a rare one. An all-new version known as Neo Geo X was released in 2012. The brand name was used as well.
In the 90s the Neo Geo was very popular in Japan, but not in the United States. We are referring to the Multi Video System. Arcade owners loved its compatibility, advanced features and the ability to run advanced and more complex games. The unit was considered as the most powerful gaming platform back then! The only reason why it wasn't popular in the United States was a high price for the games and the platform itself.
You can still play the games using emulators. The best ones are NeoRAGEx, FB Alpha and RetroArch.
Each emulator can run one of the Neo Geo ROMs available, which includes Samurai Shodown V, The King of Fighters '97, The King of Fighters Special Edition 2004, Street Hoop / Street Slam / Dunk Dream and etc.